diff --git a/changes/13926-fix-performance-regression-in-hosts-report b/changes/13926-fix-performance-regression-in-hosts-report
new file mode 100644
index 000000000..9b9e7eedd
--- /dev/null
+++ b/changes/13926-fix-performance-regression-in-hosts-report
@@ -0,0 +1,4 @@
+* Fix v4.37.0 performance regressions in the following API endpoints:
+  * `/api/v1/fleet/hosts/report`
+  * `/api/v1/fleet/hosts` when using `per_page=0` or a large number for `per_page` (in the thousands)
+* Allow specifying `disable_failing_policies` on the `/api/v1/fleet/hosts/report` API endpoint for increased performance. This is useful if the user is not interested on counting failed policies (`issues` column).
diff --git a/server/datastore/mysql/hosts.go b/server/datastore/mysql/hosts.go
index 0533b5fca..0438dac71 100644
--- a/server/datastore/mysql/hosts.go
+++ b/server/datastore/mysql/hosts.go
@@ -776,6 +776,24 @@ func amountEnrolledHostsByOSDB(ctx context.Context, db sqlx.QueryerContext) (byO
 	return byOS, totalCount, nil
 }
 
+// HostFailingPoliciesCountOptimPageSizeThreshold is the value of the page size that determines whether
+// to run an optimized version of the hosts queries when pagination is used.
+//
+// If the page size is under this value then the queries will be optimized assuming a low number of hosts.
+// If the page size is 0 or higher than this value then the queries will be optimized assuming a high number of hosts.
+//
+// IMPORTANT: The UI currently always uses PerPage=50 to list hosts. For better performance,
+// HostFailingPoliciesCountOptimPageSizeThreshold should always be higher than what the UI uses.
+//
+// The optimization consists on calculating the failing policy count (which involves querying a large table, `policy_membership`)
+// differently depending on the page size:
+//   - When the page size is short (lower than or equal to this value) then hosts are queried and filtered first, and
+//     then the failure policy count is calculated on such hosts only (with an IN clause).
+//   - When the page size is large (higher than this value) or ALL hosts are being retrieved then the hosts are
+//     filtered and their failing policy count are calculated on the same query (the IN clause performs worse
+//     than a LEFT JOIN when the number of rows is high).
+var HostFailingPoliciesCountOptimPageSizeThreshold = 100
+
 func (ds *Datastore) ListHosts(ctx context.Context, filter fleet.TeamFilter, opt fleet.HostListOptions) ([]*fleet.Host, error) {
 	sql := `SELECT
     h.id,
@@ -833,6 +851,16 @@ func (ds *Datastore) ListHosts(ctx context.Context, filter fleet.TeamFilter, opt
 		`
 	}
 
+	// See definition of HostFailingPoliciesCountOptimPageSizeThreshold for more details.
+	useHostPaginationOptim := opt.PerPage != 0 && opt.PerPage <= uint(HostFailingPoliciesCountOptimPageSizeThreshold)
+
+	if !opt.DisableFailingPolicies && !useHostPaginationOptim {
+		sql += `,
+		COALESCE(failing_policies.count, 0) AS failing_policies_count,
+		COALESCE(failing_policies.count, 0) AS total_issues_count
+		`
+	}
+
 	var params []interface{}
 
 	// Only include "additional" if filter provided.
@@ -855,14 +883,15 @@ func (ds *Datastore) ListHosts(ctx context.Context, filter fleet.TeamFilter, opt
 		    `
 	}
 
-	sql, params = ds.applyHostFilters(opt, sql, filter, params)
+	leftJoinFailingPolicies := !useHostPaginationOptim
+	sql, params = ds.applyHostFilters(opt, sql, filter, params, leftJoinFailingPolicies)
 
 	hosts := []*fleet.Host{}
 	if err := sqlx.SelectContext(ctx, ds.reader(ctx), &hosts, sql, params...); err != nil {
 		return nil, ctxerr.Wrap(ctx, err, "list hosts")
 	}
 
-	if !opt.DisableFailingPolicies {
+	if !opt.DisableFailingPolicies && useHostPaginationOptim {
 		var err error
 		hosts, err = ds.UpdatePolicyFailureCountsForHosts(ctx, hosts)
 		if err != nil {
@@ -874,7 +903,7 @@ func (ds *Datastore) ListHosts(ctx context.Context, filter fleet.TeamFilter, opt
 }
 
 // TODO(Sarah): Do we need to reconcile mutually exclusive filters?
-func (ds *Datastore) applyHostFilters(opt fleet.HostListOptions, sql string, filter fleet.TeamFilter, params []interface{}) (string, []interface{}) {
+func (ds *Datastore) applyHostFilters(opt fleet.HostListOptions, sql string, filter fleet.TeamFilter, params []interface{}, leftJoinFailingPolicies bool) (string, []interface{}) {
 	opt.OrderKey = defaultHostColumnTableAlias(opt.OrderKey)
 
 	deviceMappingJoin := `LEFT JOIN (
@@ -902,6 +931,14 @@ func (ds *Datastore) applyHostFilters(opt fleet.HostListOptions, sql string, fil
 		params = append(params, opt.SoftwareIDFilter)
 	}
 
+	failingPoliciesJoin := ""
+	if !opt.DisableFailingPolicies && leftJoinFailingPolicies {
+		failingPoliciesJoin = `LEFT JOIN (
+		    SELECT host_id, count(*) as count FROM policy_membership WHERE passes = 0
+		    GROUP BY host_id
+		) as failing_policies ON (h.id=failing_policies.host_id)`
+	}
+
 	operatingSystemJoin := ""
 	if opt.OSIDFilter != nil || (opt.OSNameFilter != nil && opt.OSVersionFilter != nil) {
 		operatingSystemJoin = `JOIN host_operating_system hos ON h.id = hos.host_id`
@@ -936,6 +973,7 @@ func (ds *Datastore) applyHostFilters(opt fleet.HostListOptions, sql string, fil
     %s
     %s
     %s
+    %s
     %s
 		WHERE TRUE AND %s AND %s AND %s AND %s
     `,
@@ -944,6 +982,7 @@ func (ds *Datastore) applyHostFilters(opt fleet.HostListOptions, sql string, fil
 		hostMDMJoin,
 		deviceMappingJoin,
 		policyMembershipJoin,
+		failingPoliciesJoin,
 		operatingSystemJoin,
 		munkiJoin,
 		displayNameJoin,
@@ -1161,12 +1200,14 @@ func filterHostsByMDMBootstrapPackageStatus(sql string, opt fleet.HostListOption
 func (ds *Datastore) CountHosts(ctx context.Context, filter fleet.TeamFilter, opt fleet.HostListOptions) (int, error) {
 	sql := `SELECT count(*) `
 
-	// ignore pagination in count
+	// Ignore pagination in count.
 	opt.Page = 0
 	opt.PerPage = 0
+	// We don't need the failing policy counts of each host for counting hosts.
+	leftJoinFailingPolicies := false
 
 	var params []interface{}
-	sql, params = ds.applyHostFilters(opt, sql, filter, params)
+	sql, params = ds.applyHostFilters(opt, sql, filter, params, leftJoinFailingPolicies)
 
 	var count int
 	if err := sqlx.GetContext(ctx, ds.reader(ctx), &count, sql, params...); err != nil {
diff --git a/server/datastore/mysql/hosts_test.go b/server/datastore/mysql/hosts_test.go
index 7e442f03c..0cc6846c2 100644
--- a/server/datastore/mysql/hosts_test.go
+++ b/server/datastore/mysql/hosts_test.go
@@ -153,6 +153,7 @@ func TestHosts(t *testing.T) {
 		{"GetMatchingHostSerials", testGetMatchingHostSerials},
 		{"ListHostsLiteByIDs", testHostsListHostsLiteByIDs},
 		{"HostScriptResult", testHostScriptResult},
+		{"ListHostsWithPagination", testListHostsWithPagination},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
@@ -7431,3 +7432,76 @@ func testHostScriptResult(t *testing.T, ds *Datastore) {
 	require.NoError(t, err)
 	require.Equal(t, expectedOutput, script.Output)
 }
+
+func testListHostsWithPagination(t *testing.T, ds *Datastore) {
+	ctx := context.Background()
+
+	newHostFunc := func(name string) *fleet.Host {
+		host, err := ds.NewHost(ctx, &fleet.Host{
+			DetailUpdatedAt: time.Now(),
+			LabelUpdatedAt:  time.Now(),
+			PolicyUpdatedAt: time.Now(),
+			SeenTime:        time.Now(),
+			NodeKey:         ptr.String(name),
+			UUID:            name,
+			Hostname:        "foo.local." + name,
+		})
+		require.NoError(t, err)
+		require.NotNil(t, host)
+		return host
+	}
+
+	filter := fleet.TeamFilter{User: test.UserAdmin}
+
+	hostCount := int(float64(HostFailingPoliciesCountOptimPageSizeThreshold) * 1.5)
+	hosts := make([]*fleet.Host, 0, hostCount)
+	for i := 0; i < hostCount; i++ {
+		hosts = append(hosts, newHostFunc(fmt.Sprintf("h%d", i)))
+	}
+
+	// List all hosts with PerPage=0 which should not use the failing policies optimization.
+	perPage0 := 0
+	hosts0, err := ds.ListHosts(ctx, filter, fleet.HostListOptions{
+		ListOptions: fleet.ListOptions{
+			PerPage: uint(perPage0),
+		},
+	})
+	require.NoError(t, err)
+	require.Len(t, hosts0, hostCount)
+	for i, host := range hosts0 {
+		require.Equal(t, host.ID, hosts[i].ID)
+	}
+
+	// List hosts with number of hosts per page equal to the failing policies optimization threshold, to
+	// (thus using the optimization).
+	perPage1 := HostFailingPoliciesCountOptimPageSizeThreshold
+	hosts1, err := ds.ListHosts(ctx, filter, fleet.HostListOptions{
+		ListOptions: fleet.ListOptions{
+			PerPage: uint(perPage1),
+		},
+	})
+	require.NoError(t, err)
+	require.Len(t, hosts1, perPage1)
+	for i, host := range hosts1 {
+		require.Equal(t, host.ID, hosts[i].ID)
+	}
+
+	// List hosts with number of hosts per page higher to the failing policies optimization threshold
+	// (thus not using the optimization)
+	perPage2 := int(float64(HostFailingPoliciesCountOptimPageSizeThreshold) * 1.2)
+	hosts2, err := ds.ListHosts(ctx, filter, fleet.HostListOptions{
+		ListOptions: fleet.ListOptions{
+			PerPage: uint(perPage2),
+		},
+	})
+	require.NoError(t, err)
+	require.Len(t, hosts2, perPage2)
+	for i, host := range hosts2 {
+		require.Equal(t, host.ID, hosts[i].ID)
+	}
+
+	// Count hosts doesn't do failing policies count or pagination.
+	count, err := ds.CountHosts(ctx, filter, fleet.HostListOptions{})
+	require.NoError(t, err)
+	require.Equal(t, hostCount, count)
+}
diff --git a/server/service/hosts.go b/server/service/hosts.go
index 85eeb010b..76e926bb4 100644
--- a/server/service/hosts.go
+++ b/server/service/hosts.go
@@ -1410,7 +1410,6 @@ func hostsReportEndpoint(ctx context.Context, request interface{}, svc fleet.Ser
 		return hostsReportResponse{Err: err}, nil
 	}
 
-	req.Opts.DisableFailingPolicies = false
 	req.Opts.AdditionalFilters = nil
 	req.Opts.Page = 0
 	req.Opts.PerPage = 0 // explicitly disable any limit, we want all matching hosts
diff --git a/server/service/integration_core_test.go b/server/service/integration_core_test.go
index de724804b..569a1652b 100644
--- a/server/service/integration_core_test.go
+++ b/server/service/integration_core_test.go
@@ -6103,7 +6103,6 @@ func (s *integrationTestSuite) TestHostsReportDownload() {
 	require.NoError(t, err)
 	require.Len(t, rows, len(hosts)+1) // all hosts + header row
 	require.Len(t, rows[0], 48)        // total number of cols
-	t.Log(rows[0])
 
 	const (
 		idCol       = 3
@@ -6198,7 +6197,6 @@ func (s *integrationTestSuite) TestHostsReportDownload() {
 	require.Equal(t, []string{"0", "TestIntegrations/TestHostsReportDownloadfoo.local1"}, rows[2][:2])
 	require.Len(t, rows[3], 3)
 	require.Equal(t, []string{"0", "TestIntegrations/TestHostsReportDownloadfoo.local0"}, rows[3][:2])
-	t.Log(rows)
 }
 
 func (s *integrationTestSuite) TestSSODisabled() {
@@ -7611,3 +7609,172 @@ func (s *integrationTestSuite) TestDirectIngestSoftwareWithInvalidFields() {
 	})
 	require.NotZero(t, wiresharkSoftware.ID)
 }
+
+func (s *integrationTestSuite) TestHostsReportWithPolicyResults() {
+	t := s.T()
+	ctx := context.Background()
+
+	newHostFunc := func(name string) *fleet.Host {
+		host, err := s.ds.NewHost(ctx, &fleet.Host{
+			DetailUpdatedAt: time.Now(),
+			LabelUpdatedAt:  time.Now(),
+			PolicyUpdatedAt: time.Now(),
+			SeenTime:        time.Now(),
+			NodeKey:         ptr.String(name),
+			UUID:            name,
+			Hostname:        "foo.local." + name,
+		})
+		require.NoError(t, err)
+		require.NotNil(t, host)
+		return host
+	}
+
+	hostCount := 10
+	hosts := make([]*fleet.Host, 0, hostCount)
+	for i := 0; i < hostCount; i++ {
+		hosts = append(hosts, newHostFunc(fmt.Sprintf("h%d", i)))
+	}
+
+	globalPolicy0, err := s.ds.NewGlobalPolicy(ctx, &test.UserAdmin.ID, fleet.PolicyPayload{
+		Name:  "foobar0",
+		Query: "SELECT 0;",
+	})
+	require.NoError(t, err)
+	globalPolicy1, err := s.ds.NewGlobalPolicy(ctx, &test.UserAdmin.ID, fleet.PolicyPayload{
+		Name:  "foobar1",
+		Query: "SELECT 1;",
+	})
+	require.NoError(t, err)
+	globalPolicy2, err := s.ds.NewGlobalPolicy(ctx, &test.UserAdmin.ID, fleet.PolicyPayload{
+		Name:  "foobar2",
+		Query: "SELECT 2;",
+	})
+	require.NoError(t, err)
+
+	for i, host := range hosts {
+		// All hosts pass the globalPolicy0
+		err := s.ds.RecordPolicyQueryExecutions(context.Background(), host, map[uint]*bool{globalPolicy0.ID: ptr.Bool(true)}, time.Now(), false)
+		require.NoError(t, err)
+
+		if i%2 == 0 {
+			// Half of the hosts pass the globalPolicy1 and fail the globalPolicy2
+			err := s.ds.RecordPolicyQueryExecutions(context.Background(), host, map[uint]*bool{globalPolicy1.ID: ptr.Bool(true)}, time.Now(), false)
+			require.NoError(t, err)
+			err = s.ds.RecordPolicyQueryExecutions(context.Background(), host, map[uint]*bool{globalPolicy2.ID: ptr.Bool(false)}, time.Now(), false)
+			require.NoError(t, err)
+		} else {
+			// Half of the hosts pass the globalPolicy2 and fail the globalPolicy1
+			err := s.ds.RecordPolicyQueryExecutions(context.Background(), host, map[uint]*bool{globalPolicy1.ID: ptr.Bool(false)}, time.Now(), false)
+			require.NoError(t, err)
+			err = s.ds.RecordPolicyQueryExecutions(context.Background(), host, map[uint]*bool{globalPolicy2.ID: ptr.Bool(true)}, time.Now(), false)
+			require.NoError(t, err)
+		}
+	}
+
+	// The hosts/report endpoint uses svc.ds.ListHosts with page=0, per_page=0, thus we are
+	// testing the non optimized for pagination queries for failing policies calculation.
+	res := s.DoRaw("GET", "/api/latest/fleet/hosts/report", nil, http.StatusOK, "format", "csv")
+	rows1, err := csv.NewReader(res.Body).ReadAll()
+	res.Body.Close()
+	require.NoError(t, err)
+	require.Len(t, rows1, len(hosts)+1) // all hosts + header row
+	require.Len(t, rows1[0], 48)        // total number of cols
+
+	var (
+		idIdx     int
+		issuesIdx int
+	)
+	for colIdx, column := range rows1[0] {
+		switch column {
+		case "issues":
+			issuesIdx = colIdx
+		case "id":
+			idIdx = colIdx
+		}
+	}
+
+	for i := 1; i < len(hosts)+1; i++ {
+		row := rows1[i]
+		require.Equal(t, row[issuesIdx], "1")
+	}
+
+	// Running with disable_failing_policies=true disable the counting of failed policies for a host.
+	// Thus, all "issues" values should be 0.
+	res = s.DoRaw("GET", "/api/latest/fleet/hosts/report", nil, http.StatusOK, "format", "csv", "disable_failing_policies", "true")
+	rows2, err := csv.NewReader(res.Body).ReadAll()
+	res.Body.Close()
+	require.NoError(t, err)
+	require.Len(t, rows2, len(hosts)+1) // all hosts + header row
+	require.Len(t, rows2[0], 48)        // total number of cols
+
+	// Check that all hosts have 0 issues and that they match the previous call to `/hosts/report`.
+	for i := 1; i < len(hosts)+1; i++ {
+		row := rows2[i]
+		require.Equal(t, row[issuesIdx], "0")
+		row1 := rows1[i]
+		require.Equal(t, row[idIdx], row1[idIdx])
+	}
+
+	for _, tc := range []struct {
+		name      string
+		args      []string
+		checkRows func(t *testing.T, rows [][]string)
+	}{
+		{
+			name: "get hosts that fail globalPolicy0",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy0.ID), "policy_response", "failure"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, 1) // just header row, all hosts pass such policy.
+			},
+		},
+		{
+			name: "get hosts that pass globalPolicy0",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy0.ID), "policy_response", "passing"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, len(hosts)+1) // all hosts + header row, all hosts pass such policy.
+			},
+		},
+		{
+			name: "get hosts that fail globalPolicy1",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy1.ID), "policy_response", "failing"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, len(hosts)/2+1) // half of hosts + header row.
+			},
+		},
+		{
+			name: "get hosts that pass globalPolicy1",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy1.ID), "policy_response", "passing"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, len(hosts)/2+1) // half of hosts + header row.
+			},
+		},
+		{
+			name: "get hosts that fail globalPolicy2",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy2.ID), "policy_response", "failing"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, len(hosts)/2+1) // half of hosts + header row.
+			},
+		},
+		{
+			name: "get hosts that pass globalPolicy2",
+			args: []string{"policy_id", fmt.Sprint(globalPolicy2.ID), "policy_response", "passing"},
+			checkRows: func(t *testing.T, rows [][]string) {
+				require.Len(t, rows, len(hosts)/2+1) // half of hosts + header row.
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			res = s.DoRaw("GET", "/api/latest/fleet/hosts/report", nil, http.StatusOK, append(tc.args, "format", "csv")...)
+			rows, err := csv.NewReader(res.Body).ReadAll()
+			res.Body.Close()
+			require.NoError(t, err)
+			tc.checkRows(t, rows)
+			// Test the same with "disable_failing_policies=true" which should not change the result.
+			res = s.DoRaw("GET", "/api/latest/fleet/hosts/report", nil, http.StatusOK, append(tc.args, "format", "csv", "disable_failing_policies", "true")...)
+			rows, err = csv.NewReader(res.Body).ReadAll()
+			res.Body.Close()
+			require.NoError(t, err)
+			tc.checkRows(t, rows)
+		})
+	}
+}