diff --git a/custom/conf/app.example.ini b/custom/conf/app.example.ini
index 473a094c4d..2a21bd64b1 100644
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@@ -1479,6 +1479,8 @@ LEVEL = Info
 ;;
 ;; Default configuration for email notifications for users (user configurable). Options: enabled, onmention, disabled
 ;DEFAULT_EMAIL_NOTIFICATIONS = enabled
+;; Send an email to all admins when a new user signs up to inform the admins about this act. Options: true, false
+;SEND_NOTIFICATION_EMAIL_ON_NEW_USER = false
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/docs/content/administration/config-cheat-sheet.en-us.md b/docs/content/administration/config-cheat-sheet.en-us.md
index 57bbc78718..eae956798f 100644
--- a/docs/content/administration/config-cheat-sheet.en-us.md
+++ b/docs/content/administration/config-cheat-sheet.en-us.md
@@ -518,6 +518,7 @@ And the following unique queues:
 
 - `DEFAULT_EMAIL_NOTIFICATIONS`: **enabled**: Default configuration for email notifications for users (user configurable). Options: enabled, onmention, disabled
 - `DISABLE_REGULAR_ORG_CREATION`: **false**: Disallow regular (non-admin) users from creating organizations.
+- `SEND_NOTIFICATION_EMAIL_ON_NEW_USER`: **false**: Send an email to all admins when a new user signs up to inform the admins about this act.
 
 ## Security (`security`)
 
diff --git a/models/user/user.go b/models/user/user.go
index 581e4a2b7b..ff197db8b3 100644
--- a/models/user/user.go
+++ b/models/user/user.go
@@ -228,6 +228,12 @@ func GetAllUsers(ctx context.Context) ([]*User, error) {
 	return users, db.GetEngine(ctx).OrderBy("id").Where("type = ?", UserTypeIndividual).Find(&users)
 }
 
+// GetAllAdmins returns a slice of all adminusers found in DB.
+func GetAllAdmins(ctx context.Context) ([]*User, error) {
+	users := make([]*User, 0)
+	return users, db.GetEngine(ctx).OrderBy("id").Where("type = ?", UserTypeIndividual).And("is_admin = ?", true).Find(&users)
+}
+
 // IsLocal returns true if user login type is LoginPlain.
 func (u *User) IsLocal() bool {
 	return u.LoginType <= auth.Plain
diff --git a/models/user/user_test.go b/models/user/user_test.go
index 65aebea43a..0e08529156 100644
--- a/models/user/user_test.go
+++ b/models/user/user_test.go
@@ -527,6 +527,16 @@ func TestIsUserVisibleToViewer(t *testing.T) {
 	test(user31, nil, false)
 }
 
+func TestGetAllAdmins(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	admins, err := user_model.GetAllAdmins(db.DefaultContext)
+	assert.NoError(t, err)
+
+	assert.Len(t, admins, 1)
+	assert.Equal(t, int64(1), admins[0].ID)
+}
+
 func Test_ValidateUser(t *testing.T) {
 	oldSetting := setting.Service.AllowedUserVisibilityModesSlice
 	defer func() {
diff --git a/modules/setting/admin.go b/modules/setting/admin.go
index 2d2dd26de9..d7f0ee827d 100644
--- a/modules/setting/admin.go
+++ b/modules/setting/admin.go
@@ -5,8 +5,9 @@ package setting
 
 // Admin settings
 var Admin struct {
-	DisableRegularOrgCreation bool
-	DefaultEmailNotification  string
+	DisableRegularOrgCreation      bool
+	DefaultEmailNotification       string
+	SendNotificationEmailOnNewUser bool
 }
 
 func loadAdminFrom(rootCfg ConfigProvider) {
diff --git a/routers/web/auth/auth.go b/routers/web/auth/auth.go
index 9bc7566432..e86c5da3eb 100644
--- a/routers/web/auth/auth.go
+++ b/routers/web/auth/auth.go
@@ -32,6 +32,7 @@ import (
 	"code.gitea.io/gitea/services/externalaccount"
 	"code.gitea.io/gitea/services/forms"
 	"code.gitea.io/gitea/services/mailer"
+	notify_service "code.gitea.io/gitea/services/notify"
 
 	"github.com/markbates/goth"
 )
@@ -600,6 +601,7 @@ func handleUserCreated(ctx *context.Context, u *user_model.User, gothUser *goth.
 		}
 	}
 
+	notify_service.NewUserSignUp(ctx, u)
 	// update external user information
 	if gothUser != nil {
 		if err := externalaccount.UpdateExternalUser(ctx, u, *gothUser); err != nil {
diff --git a/services/mailer/mail_admin_new_user.go b/services/mailer/mail_admin_new_user.go
new file mode 100644
index 0000000000..e9610e626a
--- /dev/null
+++ b/services/mailer/mail_admin_new_user.go
@@ -0,0 +1,81 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+package mailer
+
+import (
+	"bytes"
+	"context"
+	"strconv"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/templates"
+	"code.gitea.io/gitea/modules/translation"
+)
+
+const (
+	tplNewUserMail base.TplName = "notify/admin_new_user"
+)
+
+var sa = SendAsync
+
+// MailNewUser sends notification emails on new user registrations to all admins
+func MailNewUser(ctx context.Context, u *user_model.User) {
+	if !setting.Admin.SendNotificationEmailOnNewUser {
+		return
+	}
+
+	if setting.MailService == nil {
+		// No mail service configured
+		return
+	}
+
+	recipients, err := user_model.GetAllAdmins(ctx)
+	if err != nil {
+		log.Error("user_model.GetAllAdmins: %v", err)
+		return
+	}
+
+	langMap := make(map[string][]string)
+	for _, r := range recipients {
+		langMap[r.Language] = append(langMap[r.Language], r.Email)
+	}
+
+	for lang, tos := range langMap {
+		mailNewUser(ctx, u, lang, tos)
+	}
+}
+
+func mailNewUser(ctx context.Context, u *user_model.User, lang string, tos []string) {
+	locale := translation.NewLocale(lang)
+
+	manageUserURL := setting.AppURL + "admin/users/" + strconv.FormatInt(u.ID, 10)
+	subject := locale.Tr("mail.admin.new_user.subject", u.Name)
+	body := locale.Tr("mail.admin.new_user.text", manageUserURL)
+	mailMeta := map[string]any{
+		"NewUser":    u,
+		"NewUserUrl": u.HTMLURL(),
+		"Subject":    subject,
+		"Body":       body,
+		"Language":   locale.Language(),
+		"Locale":     locale,
+		"Str2html":   templates.Str2html,
+	}
+
+	var mailBody bytes.Buffer
+
+	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplNewUserMail), mailMeta); err != nil {
+		log.Error("ExecuteTemplate [%s]: %v", string(tplNewUserMail)+"/body", err)
+		return
+	}
+
+	msgs := make([]*Message, 0, len(tos))
+	for _, to := range tos {
+		msg := NewMessage(to, subject, mailBody.String())
+		msg.Info = subject
+		msgs = append(msgs, msg)
+	}
+	sa(msgs...)
+}
diff --git a/services/mailer/mail_admin_new_user_test.go b/services/mailer/mail_admin_new_user_test.go
new file mode 100644
index 0000000000..b89d888ee1
--- /dev/null
+++ b/services/mailer/mail_admin_new_user_test.go
@@ -0,0 +1,98 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package mailer
+
+import (
+	"context"
+	"strconv"
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/translation"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func getTestUsers(t *testing.T) []*user_model.User {
+	t.Helper()
+	admin := new(user_model.User)
+	admin.Name = "testadmin"
+	admin.IsAdmin = true
+	admin.Language = "en_US"
+	admin.Email = "admin@example.com"
+	require.NoError(t, user_model.CreateUser(db.DefaultContext, admin))
+
+	newUser := new(user_model.User)
+	newUser.Name = "new_user"
+	newUser.Language = "en_US"
+	newUser.IsAdmin = false
+	newUser.Email = "new_user@example.com"
+	newUser.LastLoginUnix = 1693648327
+	newUser.CreatedUnix = 1693648027
+	require.NoError(t, user_model.CreateUser(db.DefaultContext, newUser))
+
+	return []*user_model.User{admin, newUser}
+}
+
+func cleanUpUsers(ctx context.Context, users []*user_model.User) {
+	for _, u := range users {
+		db.DeleteByID[user_model.User](ctx, u.ID)
+	}
+}
+
+func TestAdminNotificationMail_test(t *testing.T) {
+	translation.InitLocales(context.Background())
+	locale := translation.NewLocale("")
+	key := "mail.admin.new_user.user_info"
+	translatedKey := locale.Tr(key)
+	require.NotEqualValues(t, key, translatedKey)
+
+	mailService := setting.Mailer{
+		From:     "test@example.com",
+		Protocol: "dummy",
+	}
+
+	setting.MailService = &mailService
+
+	// test with SEND_NOTIFICATION_EMAIL_ON_NEW_USER enabled
+	setting.Admin.SendNotificationEmailOnNewUser = true
+
+	ctx := context.Background()
+	NewContext(ctx)
+
+	users := getTestUsers(t)
+	oldSendAsync := sa
+	defer func() {
+		sa = oldSendAsync
+		cleanUpUsers(ctx, users)
+	}()
+
+	called := false
+	sa = func(msgs ...*Message) {
+		assert.Equal(t, len(msgs), 1, "Test provides only one admin user, so only one email must be sent")
+		assert.Equal(t, msgs[0].To, users[0].Email, "checks if the recipient is the admin of the instance")
+		manageUserURL := setting.AppURL + "admin/users/" + strconv.FormatInt(users[1].ID, 10)
+		assert.Contains(t, msgs[0].Body, manageUserURL)
+		assert.Contains(t, msgs[0].Body, users[1].HTMLURL())
+		assert.Contains(t, msgs[0].Body, translatedKey, "the .Locale translates to nothing")
+		assert.Contains(t, msgs[0].Body, users[1].Name, "user name of the newly created user")
+		for _, untranslated := range []string{"mail.admin", "admin.users"} {
+			assert.NotContains(t, msgs[0].Body, untranslated, "this is an untranslated placeholder prefix")
+		}
+		called = true
+	}
+	MailNewUser(ctx, users[1])
+	assert.True(t, called)
+
+	// test with SEND_NOTIFICATION_EMAIL_ON_NEW_USER disabled; emails shouldn't be sent
+	setting.Admin.SendNotificationEmailOnNewUser = false
+	sa = func(msgs ...*Message) {
+		assert.Equal(t, 1, 0, "this shouldn't execute. MailNewUser must exit early since SEND_NOTIFICATION_EMAIL_ON_NEW_USER is disabled")
+	}
+
+	MailNewUser(ctx, users[1])
+}
diff --git a/services/mailer/notify.go b/services/mailer/notify.go
index cc4e6baf0b..5c6e635b7a 100644
--- a/services/mailer/notify.go
+++ b/services/mailer/notify.go
@@ -202,3 +202,7 @@ func (m *mailNotifier) RepoPendingTransfer(ctx context.Context, doer, newOwner *
 		log.Error("SendRepoTransferNotifyMail: %v", err)
 	}
 }
+
+func (m *mailNotifier) NewUserSignUp(ctx context.Context, newUser *user_model.User) {
+	MailNewUser(ctx, newUser)
+}
diff --git a/services/notify/notifier.go b/services/notify/notifier.go
index ed053a812a..3230a5e5f5 100644
--- a/services/notify/notifier.go
+++ b/services/notify/notifier.go
@@ -59,6 +59,8 @@ type Notifier interface {
 	EditWikiPage(ctx context.Context, doer *user_model.User, repo *repo_model.Repository, page, comment string)
 	DeleteWikiPage(ctx context.Context, doer *user_model.User, repo *repo_model.Repository, page string)
 
+	NewUserSignUp(ctx context.Context, newUser *user_model.User)
+
 	NewRelease(ctx context.Context, rel *repo_model.Release)
 	UpdateRelease(ctx context.Context, doer *user_model.User, rel *repo_model.Release)
 	DeleteRelease(ctx context.Context, doer *user_model.User, rel *repo_model.Release)
diff --git a/services/notify/notify.go b/services/notify/notify.go
index 16fbb6325d..9cb329d302 100644
--- a/services/notify/notify.go
+++ b/services/notify/notify.go
@@ -347,6 +347,13 @@ func RepoPendingTransfer(ctx context.Context, doer, newOwner *user_model.User, r
 	}
 }
 
+// NewUserSignUp notifies about a newly signed up user to notifiers
+func NewUserSignUp(ctx context.Context, newUser *user_model.User) {
+	for _, notifier := range notifiers {
+		notifier.NewUserSignUp(ctx, newUser)
+	}
+}
+
 // PackageCreate notifies creation of a package to notifiers
 func PackageCreate(ctx context.Context, doer *user_model.User, pd *packages_model.PackageDescriptor) {
 	for _, notifier := range notifiers {
diff --git a/services/notify/null.go b/services/notify/null.go
index dddd421bef..894d118eac 100644
--- a/services/notify/null.go
+++ b/services/notify/null.go
@@ -197,6 +197,9 @@ func (*NullNotifier) SyncDeleteRef(ctx context.Context, doer *user_model.User, r
 func (*NullNotifier) RepoPendingTransfer(ctx context.Context, doer, newOwner *user_model.User, repo *repo_model.Repository) {
 }
 
+func (*NullNotifier) NewUserSignUp(ctx context.Context, newUser *user_model.User) {
+}
+
 // PackageCreate places a place holder function
 func (*NullNotifier) PackageCreate(ctx context.Context, doer *user_model.User, pd *packages_model.PackageDescriptor) {
 }
diff --git a/templates/mail/notify/admin_new_user.tmpl b/templates/mail/notify/admin_new_user.tmpl
new file mode 100644
index 0000000000..34d1584f60
--- /dev/null
+++ b/templates/mail/notify/admin_new_user.tmpl
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+	<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+	<title>{{.Subject}}</title>
+
+	<style>
+		blockquote { padding-left: 1em; margin: 1em 0; border-left: 1px solid grey; color: #777}
+		.footer { font-size:small; color:#666;}
+	</style>
+
+</head>
+
+<body>
+	<ul>
+		<h3>{{.Locale.Tr "mail.admin.new_user.user_info" | Str2html}}: <a href="{{.NewUserUrl}}">@{{.NewUser.Name}}</a></h3>
+		<li>{{.Locale.Tr "admin.users.created" | Str2html}}: {{DateTime "full" .NewUser.CreatedUnix}}</li>
+	</ul>
+	<p> {{.Body | Str2html}} </p>
+</body>
+</html>