diff --git a/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/16_plus/get_ctypes.sql b/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/16_plus/get_ctypes.sql
index 8a5347a4070..cd1ed28af9f 100644
--- a/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/16_plus/get_ctypes.sql
+++ b/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/16_plus/get_ctypes.sql
@@ -1,8 +1,8 @@
-SELECT CASE WHEN datlocprovider = 'i' THEN
-	(SELECT daticulocale as cname FROM pg_catalog.pg_database WHERE datname = current_database())
-ELSE
-    (SELECT datcollate as cname FROM pg_catalog.pg_database WHERE datname = current_database()
-    UNION
-    SELECT datctype as cname FROM pg_catalog.pg_database WHERE datname = current_database())
-END
-FROM pg_catalog.pg_database WHERE datname = current_database();
+SELECT daticulocale AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider = 'i'
+UNION
+SELECT datcollate AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider <> 'i'
+UNION
+SELECT datctype AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider <> 'i';
diff --git a/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/17_plus/get_ctypes.sql b/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/17_plus/get_ctypes.sql
index 00221883616..9a06912091a 100644
--- a/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/17_plus/get_ctypes.sql
+++ b/web/pgadmin/browser/server_groups/servers/databases/templates/databases/sql/17_plus/get_ctypes.sql
@@ -1,8 +1,11 @@
-SELECT CASE WHEN datlocprovider = 'i' THEN
-	(SELECT datlocale as cname FROM pg_catalog.pg_database WHERE datname = current_database())
-ELSE
-    (SELECT datcollate as cname FROM pg_catalog.pg_database WHERE datname = current_database()
-    UNION
-    SELECT datctype as cname FROM pg_catalog.pg_database WHERE datname = current_database())
-END
-FROM pg_catalog.pg_database WHERE datname = current_database();
+{# Both the ICU and the builtin provider keep the locale in datlocale; only a
+   libc database collates according to datcollate and datctype, which a
+   builtin database merely inherits from its template. #}
+SELECT datlocale AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider IN ('i', 'b')
+UNION
+SELECT datcollate AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider = 'c'
+UNION
+SELECT datctype AS cname FROM pg_catalog.pg_database
+WHERE datname = current_database() AND datlocprovider = 'c';
diff --git a/web/pgadmin/browser/server_groups/servers/databases/tests/test_db_get_ctypes.py b/web/pgadmin/browser/server_groups/servers/databases/tests/test_db_get_ctypes.py
new file mode 100644
index 00000000000..354f5941368
--- /dev/null
+++ b/web/pgadmin/browser/server_groups/servers/databases/tests/test_db_get_ctypes.py
@@ -0,0 +1,152 @@
+##########################################################################
+#
+# pgAdmin 4 - PostgreSQL Tools
+#
+# Copyright (C) 2013 - 2026, The pgAdmin Development Team
+# This software is released under the PostgreSQL Licence
+#
+##########################################################################
+
+"""Tests for the get_ctypes.sql templates (#9798).
+
+The query feeding the collation and character type fields of the Database
+dialog has to report the locale the database actually uses, which depends on
+its locale provider: datcollate and datctype for libc, and datlocale for both
+ICU and the builtin provider introduced in PostgreSQL 17. A builtin database
+still carries the collation it inherited from its template, so reading
+datcollate for it reports a locale that is not in use.
+
+The query is executed here through the versioned template loader, so the test
+also covers the server version picking the right template bucket.
+"""
+
+import uuid
+
+from flask import render_template
+
+from pgadmin.utils.route import BaseTestGenerator
+from regression.python_test_utils import test_utils as utils
+
+DEFAULTS = ('C', 'POSIX')
+
+
+class GetCtypesTestCase(BaseTestGenerator):
+    """get_ctypes.sql must report the locale in use, per locale provider."""
+
+    scenarios = [
+        ('libc reports the collation', dict(
+            provider='libc', swapped=False)),
+        ('libc reports the character type', dict(
+            provider='libc', swapped=True)),
+        ('The builtin provider reports its own locale', dict(
+            provider='builtin', swapped=False)),
+        ('ICU reports the ICU locale', dict(
+            provider='icu', swapped=False)),
+    ]
+
+    def setUp(self):
+        # No pgAdmin server registration needed: this exercises the SQL, so
+        # it talks to the server directly.
+        self.db_name = None
+        self.connection = self._connect('postgres')
+        cursor = self.connection.cursor()
+        cursor.execute("SELECT current_setting('server_version_num')::int")
+        self.server_version = cursor.fetchone()[0]
+        cursor.execute("SELECT datcollate, pg_encoding_to_char(encoding) "
+                       "FROM pg_catalog.pg_database WHERE datname = "
+                       "'template0'")
+        self.template_collate, self.template_encoding = cursor.fetchone()
+
+    def _connect(self, db_name):
+        return utils.get_db_connection(db_name,
+                                       self.server['username'],
+                                       self.server['db_password'],
+                                       self.server['host'],
+                                       self.server['port'],
+                                       self.server['sslmode'])
+
+    def _create_database(self, options):
+        self.db_name = 'test_ctypes_%s' % str(uuid.uuid4())[1:8]
+        old_isolation_level = self.connection.isolation_level
+        utils.set_isolation_level(self.connection, 0)
+        cursor = self.connection.cursor()
+        cursor.execute('CREATE DATABASE "%s" TEMPLATE template0 %s' % (
+            self.db_name, options))
+        utils.set_isolation_level(self.connection, old_isolation_level)
+        self.connection.commit()
+
+    def _reported_locales(self):
+        """Run the versioned get_ctypes.sql against the new database."""
+        template_path = 'databases/sql/#{0}#'.format(self.server_version)
+        with self.app.app_context():
+            sql = render_template("/".join([template_path, 'get_ctypes.sql']))
+
+        connection = self._connect(self.db_name)
+        try:
+            cursor = connection.cursor()
+            cursor.execute(sql)
+            return [row[0] for row in cursor.fetchall()]
+        finally:
+            connection.close()
+
+    def _skip_unless_distinct_template_locale(self):
+        if self.template_collate in DEFAULTS:
+            self.skipTest(
+                "template0 uses the '%s' locale, so a database with a "
+                "collation distinguishable from the defaults cannot be "
+                "created here." % self.template_collate)
+
+    def runTest(self):
+        if self.provider == 'libc':
+            self._skip_unless_distinct_template_locale()
+            # Set exactly one of the two to the template locale, so that the
+            # value proves which of datcollate and datctype was reported.
+            collate, ctype = ('C', self.template_collate) if self.swapped \
+                else (self.template_collate, 'C')
+            self._create_database(
+                "LC_COLLATE '%s' LC_CTYPE '%s'" % (collate, ctype))
+            self.assertIn(self.template_collate, self._reported_locales())
+            return
+
+        if self.provider == 'builtin':
+            if self.server_version < 170000:
+                self.skipTest('The builtin locale provider requires '
+                              'PostgreSQL 17 or later.')
+            if self.template_encoding != 'UTF8':
+                self.skipTest("template0 is %s encoded, so a UTF-8 builtin "
+                              "locale cannot be used here."
+                              % self.template_encoding)
+            if self.template_collate == 'C.UTF-8':
+                self.skipTest("template0 already uses the 'C.UTF-8' locale, "
+                              "the only one a UTF-8 builtin database can "
+                              "use, so a distinguishable one cannot be "
+                              "created here.")
+            self._skip_unless_distinct_template_locale()
+            self._create_database("LOCALE_PROVIDER builtin "
+                                  "BUILTIN_LOCALE 'C.UTF-8' ENCODING UTF8")
+
+            reported = self._reported_locales()
+            self.assertIn('C.UTF-8', reported)
+            # datcollate is inherited from the template and is not the locale
+            # this database collates with, so it must not be offered.
+            self.assertNotIn(self.template_collate, reported)
+            return
+
+        # ICU
+        if self.server_version < 150000:
+            self.skipTest('LOCALE_PROVIDER icu requires PostgreSQL 15 or '
+                          'later.')
+        cursor = self.connection.cursor()
+        cursor.execute("SELECT 1 FROM pg_catalog.pg_collation "
+                       "WHERE collprovider = 'i' LIMIT 1")
+        if cursor.fetchone() is None:
+            self.skipTest('This server was built without ICU support.')
+        self._create_database(
+            "LOCALE_PROVIDER icu ICU_LOCALE 'en-GB' LC_COLLATE '%s' "
+            "LC_CTYPE '%s'" % (self.template_collate, self.template_collate))
+        self.assertIn('en-GB', self._reported_locales())
+
+    def tearDown(self):
+        if self.db_name:
+            utils.drop_database(self.connection, self.db_name)
+        self.connection.close()