diff --git a/github/enterprise_apps.go b/github/enterprise_apps.go
new file mode 100644
index 00000000000..2e43a142305
--- /dev/null
+++ b/github/enterprise_apps.go
@@ -0,0 +1,116 @@
+// Copyright 2025 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package github
+
+import (
+	"context"
+	"fmt"
+)
+
+// EnterpriseInstallationRepositoriesOptions specifies the parameters for
+// EnterpriseService.AddRepositoriesToInstallation and
+// EnterpriseService.RemoveRepositoriesFromInstallation.
+type EnterpriseInstallationRepositoriesOptions struct {
+	SelectedRepositoryIDs []int64 `json:"selected_repository_ids"`
+}
+
+// EnterpriseInstallationRepositoriesToggleOptions specifies the parameters for
+// EnterpriseService.ToggleInstallationRepositories.
+type EnterpriseInstallationRepositoriesToggleOptions struct {
+	RepositorySelection   *string `json:"repository_selection,omitempty"` // Can be "all" or "selected"
+	SelectedRepositoryIDs []int64 `json:"selected_repository_ids,omitempty"`
+}
+
+// ListRepositoriesForOrgInstallation lists the repositories that an enterprise app installation
+// has access to on an organization.
+//
+// GitHub API docs: https://docs.github.com/enterprise-cloud@latest/rest/enterprise-admin/organization-installations#get-the-repositories-accessible-to-a-given-github-app-installation
+//
+//meta:operation GET /enterprises/{enterprise}/apps/organizations/{org}/installations/{installation_id}/repositories
+func (s *EnterpriseService) ListRepositoriesForOrgInstallation(ctx context.Context, enterprise, org string, installationID int64, opts *ListOptions) (*ListRepositories, *Response, error) {
+	u := fmt.Sprintf("enterprises/%v/apps/organizations/%v/installations/%v/repositories", enterprise, org, installationID)
+	u, err := addOptions(u, opts)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	req, err := s.client.NewRequest("GET", u, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var r *ListRepositories
+	resp, err := s.client.Do(ctx, req, &r)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return r, resp, nil
+}
+
+// ToggleInstallationRepositories changes a GitHub App installation's repository access
+// between all repositories and a selected set.
+//
+// GitHub API docs: https://docs.github.com/enterprise-cloud@latest/rest/enterprise-admin/organization-installations#toggle-installation-repository-access-between-selected-and-all-repositories
+//
+//meta:operation PATCH /enterprises/{enterprise}/apps/organizations/{org}/installations/{installation_id}/repositories
+func (s *EnterpriseService) ToggleInstallationRepositories(ctx context.Context, enterprise, org string, installationID int64, opts *EnterpriseInstallationRepositoriesToggleOptions) (*ListRepositories, *Response, error) {
+	u := fmt.Sprintf("enterprises/%v/apps/organizations/%v/installations/%v/repositories", enterprise, org, installationID)
+	req, err := s.client.NewRequest("PATCH", u, opts)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var r *ListRepositories
+	resp, err := s.client.Do(ctx, req, &r)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return r, resp, nil
+}
+
+// AddRepositoriesToInstallation grants repository access for a GitHub App installation.
+//
+// GitHub API docs: https://docs.github.com/enterprise-cloud@latest/rest/enterprise-admin/organization-installations#grant-repository-access-to-an-organization-installation
+//
+//meta:operation PATCH /enterprises/{enterprise}/apps/organizations/{org}/installations/{installation_id}/repositories/add
+func (s *EnterpriseService) AddRepositoriesToInstallation(ctx context.Context, enterprise, org string, installationID int64, opts EnterpriseInstallationRepositoriesOptions) (*ListRepositories, *Response, error) {
+	u := fmt.Sprintf("enterprises/%v/apps/organizations/%v/installations/%v/repositories/add", enterprise, org, installationID)
+	req, err := s.client.NewRequest("PATCH", u, opts)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var r *ListRepositories
+	resp, err := s.client.Do(ctx, req, &r)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return r, resp, nil
+}
+
+// RemoveRepositoriesFromInstallation revokes repository access from a GitHub App installation.
+//
+// GitHub API docs: https://docs.github.com/enterprise-cloud@latest/rest/enterprise-admin/organization-installations#remove-repository-access-from-an-organization-installation
+//
+//meta:operation PATCH /enterprises/{enterprise}/apps/organizations/{org}/installations/{installation_id}/repositories/remove
+func (s *EnterpriseService) RemoveRepositoriesFromInstallation(ctx context.Context, enterprise, org string, installationID int64, opts EnterpriseInstallationRepositoriesOptions) (*ListRepositories, *Response, error) {
+	u := fmt.Sprintf("enterprises/%v/apps/organizations/%v/installations/%v/repositories/remove", enterprise, org, installationID)
+	req, err := s.client.NewRequest("PATCH", u, opts)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var r *ListRepositories
+	resp, err := s.client.Do(ctx, req, &r)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	return r, resp, nil
+}
diff --git a/github/enterprise_apps_test.go b/github/enterprise_apps_test.go
new file mode 100644
index 00000000000..29a58e0439d
--- /dev/null
+++ b/github/enterprise_apps_test.go
@@ -0,0 +1,155 @@
+// Copyright 2025 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package github
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestEnterpriseService_ListRepositoriesForOrgInstallation(t *testing.T) {
+	t.Parallel()
+	client, mux, _ := setup(t)
+
+	mux.HandleFunc("/enterprises/e/apps/organizations/o/installations/1/repositories", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "GET")
+		testFormValues(t, r, values{"page": "1"})
+		fmt.Fprint(w, `{"total_count":1, "repositories":[{"id":1}]}`)
+	})
+
+	ctx := t.Context()
+	repos, _, err := client.Enterprise.ListRepositoriesForOrgInstallation(ctx, "e", "o", 1, &ListOptions{Page: 1})
+	if err != nil {
+		t.Errorf("Enterprise.ListRepositoriesForOrgInstallation returned error: %v", err)
+	}
+
+	want := &ListRepositories{TotalCount: Ptr(1), Repositories: []*Repository{{ID: Ptr(int64(1))}}}
+	if diff := cmp.Diff(repos, want); diff != "" {
+		t.Errorf("Enterprise.ListRepositoriesForOrgInstallation returned diff (-want +got):\n%v", diff)
+	}
+
+	const methodName = "ListRepositoriesForOrgInstallation"
+	testBadOptions(t, methodName, func() (err error) {
+		_, _, err = client.Enterprise.ListRepositoriesForOrgInstallation(ctx, "\n", "\n", -1, &ListOptions{})
+		return err
+	})
+
+	testNewRequestAndDoFailure(t, methodName, client, func() (*Response, error) {
+		_, resp, err := client.Enterprise.ListRepositoriesForOrgInstallation(ctx, "e", "o", 1, &ListOptions{})
+		return resp, err
+	})
+}
+
+func TestEnterpriseService_ToggleInstallationRepositories(t *testing.T) {
+	t.Parallel()
+	client, mux, _ := setup(t)
+
+	input := &EnterpriseInstallationRepositoriesToggleOptions{
+		RepositorySelection:   String("selected"),
+		SelectedRepositoryIDs: []int64{1, 2},
+	}
+
+	mux.HandleFunc("/enterprises/e/apps/organizations/o/installations/1/repositories", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "PATCH")
+		testBody(t, r, `{"repository_selection":"selected","selected_repository_ids":[1,2]}`+"\n")
+		fmt.Fprint(w, `{"total_count":2, "repositories":[{"id":1},{"id":2}]}`)
+	})
+
+	ctx := t.Context()
+	repos, _, err := client.Enterprise.ToggleInstallationRepositories(ctx, "e", "o", 1, input)
+	if err != nil {
+		t.Errorf("Enterprise.ToggleInstallationRepositories returned error: %v", err)
+	}
+
+	want := &ListRepositories{TotalCount: Ptr(2), Repositories: []*Repository{{ID: Ptr(int64(1))}, {ID: Ptr(int64(2))}}}
+	if diff := cmp.Diff(repos, want); diff != "" {
+		t.Errorf("Enterprise.ToggleInstallationRepositories returned diff (-want +got):\n%v", diff)
+	}
+
+	const methodName = "ToggleInstallationRepositories"
+	testBadOptions(t, methodName, func() (err error) {
+		_, _, err = client.Enterprise.ToggleInstallationRepositories(ctx, "\n", "\n", -1, input)
+		return err
+	})
+
+	testNewRequestAndDoFailure(t, methodName, client, func() (*Response, error) {
+		_, resp, err := client.Enterprise.ToggleInstallationRepositories(ctx, "e", "o", 1, input)
+		return resp, err
+	})
+}
+
+func TestEnterpriseService_AddRepositoriesToInstallation(t *testing.T) {
+	t.Parallel()
+	client, mux, _ := setup(t)
+
+	input := EnterpriseInstallationRepositoriesOptions{SelectedRepositoryIDs: []int64{1, 2}}
+
+	mux.HandleFunc("/enterprises/e/apps/organizations/o/installations/1/repositories/add", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "PATCH")
+		testBody(t, r, `{"selected_repository_ids":[1,2]}`+"\n")
+		fmt.Fprint(w, `{"total_count":2, "repositories":[{"id":1},{"id":2}]}`)
+	})
+
+	ctx := t.Context()
+	repos, _, err := client.Enterprise.AddRepositoriesToInstallation(ctx, "e", "o", 1, input)
+	if err != nil {
+		t.Errorf("Enterprise.AddRepositoriesToInstallation returned error: %v", err)
+	}
+
+	want := &ListRepositories{TotalCount: Ptr(2), Repositories: []*Repository{{ID: Ptr(int64(1))}, {ID: Ptr(int64(2))}}}
+	if diff := cmp.Diff(repos, want); diff != "" {
+		t.Errorf("Enterprise.AddRepositoriesToInstallation returned diff (-want +got):\n%v", diff)
+	}
+
+	const methodName = "AddRepositoriesToInstallation"
+	testBadOptions(t, methodName, func() (err error) {
+		_, _, err = client.Enterprise.AddRepositoriesToInstallation(ctx, "\n", "\n", -1, input)
+		return err
+	})
+
+	testNewRequestAndDoFailure(t, methodName, client, func() (*Response, error) {
+		_, resp, err := client.Enterprise.AddRepositoriesToInstallation(ctx, "e", "o", 1, input)
+		return resp, err
+	})
+}
+
+func TestEnterpriseService_RemoveRepositoriesFromInstallation(t *testing.T) {
+	t.Parallel()
+	client, mux, _ := setup(t)
+
+	input := EnterpriseInstallationRepositoriesOptions{SelectedRepositoryIDs: []int64{1, 2}}
+
+	mux.HandleFunc("/enterprises/e/apps/organizations/o/installations/1/repositories/remove", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "PATCH")
+		testBody(t, r, `{"selected_repository_ids":[1,2]}`+"\n")
+		fmt.Fprint(w, `{"total_count":2, "repositories":[{"id":1},{"id":2}]}`)
+	})
+
+	ctx := t.Context()
+	repos, _, err := client.Enterprise.RemoveRepositoriesFromInstallation(ctx, "e", "o", 1, input)
+	if err != nil {
+		t.Errorf("Enterprise.RemoveRepositoriesFromInstallation returned error: %v", err)
+	}
+
+	want := &ListRepositories{TotalCount: Ptr(2), Repositories: []*Repository{{ID: Ptr(int64(1))}, {ID: Ptr(int64(2))}}}
+	if diff := cmp.Diff(repos, want); diff != "" {
+		t.Errorf("Enterprise.RemoveRepositoriesFromInstallation returned diff (-want +got):\n%v", diff)
+	}
+
+	const methodName = "RemoveRepositoriesFromInstallation"
+	testBadOptions(t, methodName, func() (err error) {
+		_, _, err = client.Enterprise.RemoveRepositoriesFromInstallation(ctx, "\n", "\n", -1, input)
+		return err
+	})
+
+	testNewRequestAndDoFailure(t, methodName, client, func() (*Response, error) {
+		_, resp, err := client.Enterprise.RemoveRepositoriesFromInstallation(ctx, "e", "o", 1, input)
+		return resp, err
+	})
+}
diff --git a/github/github-accessors.go b/github/github-accessors.go
index 2a1a9394f67..ef96f32570b 100644
--- a/github/github-accessors.go
+++ b/github/github-accessors.go
@@ -9254,6 +9254,14 @@ func (e *EnterpriseCustomPropertiesValues) GetOrganizationLogin() string {
 	return *e.OrganizationLogin
 }
 
+// GetRepositorySelection returns the RepositorySelection field if it's non-nil, zero value otherwise.
+func (e *EnterpriseInstallationRepositoriesToggleOptions) GetRepositorySelection() string {
+	if e == nil || e.RepositorySelection == nil {
+		return ""
+	}
+	return *e.RepositorySelection
+}
+
 // GetEnterpriseServerUser returns the EnterpriseServerUser field if it's non-nil, zero value otherwise.
 func (e *EnterpriseLicensedUsers) GetEnterpriseServerUser() bool {
 	if e == nil || e.EnterpriseServerUser == nil {
diff --git a/github/github-accessors_test.go b/github/github-accessors_test.go
index c926697944f..8e39eab64f3 100644
--- a/github/github-accessors_test.go
+++ b/github/github-accessors_test.go
@@ -11985,6 +11985,17 @@ func TestEnterpriseCustomPropertiesValues_GetOrganizationLogin(tt *testing.T) {
 	e.GetOrganizationLogin()
 }
 
+func TestEnterpriseInstallationRepositoriesToggleOptions_GetRepositorySelection(tt *testing.T) {
+	tt.Parallel()
+	var zeroValue string
+	e := &EnterpriseInstallationRepositoriesToggleOptions{RepositorySelection: &zeroValue}
+	e.GetRepositorySelection()
+	e = &EnterpriseInstallationRepositoriesToggleOptions{}
+	e.GetRepositorySelection()
+	e = nil
+	e.GetRepositorySelection()
+}
+
 func TestEnterpriseLicensedUsers_GetEnterpriseServerUser(tt *testing.T) {
 	tt.Parallel()
 	var zeroValue bool