diff --git a/autotest/ogr/ogr_sql_test.py b/autotest/ogr/ogr_sql_test.py
index 1e4f31bfa449..330b27df7789 100755
--- a/autotest/ogr/ogr_sql_test.py
+++ b/autotest/ogr/ogr_sql_test.py
@@ -151,6 +151,32 @@ def data_ds():
         yield ds
 
 
+###############################################################################
+# Test an unrecognized dialect name
+
+
+def test_ogr_sql_unrecognized_dialect(data_ds):
+    class MyHandler:
+        def __init__(self):
+            self.warning_raised = False
+
+        def callback(self, err_type, err_no, err_msg):
+            if (
+                err_type == gdal.CE_Warning
+                and err_msg
+                == "Dialect 'unknown' is unsupported. Only supported dialects are 'OGRSQL', 'SQLITE'. Defaulting to OGRSQL"
+            ):
+                self.warning_raised = True
+
+    my_error_handler = MyHandler()
+    with gdaltest.error_handler(my_error_handler.callback):
+        with data_ds.ExecuteSQL(
+            "SELECT * FROM poly WHERE eas_id < 167", dialect="unknown"
+        ) as sql_lyr:
+            assert sql_lyr.GetFeatureCount(force=1) == 3
+    assert my_error_handler.warning_raised
+
+
 ###############################################################################
 # Test a simple query with a where clause.
 
diff --git a/gcore/gdaldataset.cpp b/gcore/gdaldataset.cpp
index 1b622ed06d03..f359c4b9b3b6 100644
--- a/gcore/gdaldataset.cpp
+++ b/gcore/gdaldataset.cpp
@@ -6478,6 +6478,36 @@ GDALDataset::ExecuteSQL(const char *pszStatement, OGRGeometry *poSpatialFilter,
 #endif
     }
 
+    if (pszDialect != nullptr && !EQUAL(pszDialect, "") &&
+        !EQUAL(pszDialect, "OGRSQL"))
+    {
+        std::string osDialectList = "'OGRSQL'";
+#ifdef SQLITE_ENABLED
+        osDialectList += ", 'SQLITE'";
+#endif
+        const char *pszDialects =
+            GetMetadataItem(GDAL_DMD_SUPPORTED_SQL_DIALECTS);
+        if (pszDialects)
+        {
+            const CPLStringList aosTokens(
+                CSLTokenizeString2(pszDialects, " ", 0));
+            for (int i = 0; i < aosTokens.size(); ++i)
+            {
+                if (!EQUAL(aosTokens[i], "OGRSQL") &&
+                    !EQUAL(aosTokens[i], "SQLITE"))
+                {
+                    osDialectList += ", '";
+                    osDialectList += aosTokens[i];
+                    osDialectList += "'";
+                }
+            }
+        }
+        CPLError(CE_Warning, CPLE_NotSupported,
+                 "Dialect '%s' is unsupported. Only supported dialects are %s. "
+                 "Defaulting to OGRSQL",
+                 pszDialect, osDialectList.c_str());
+    }
+
     /* -------------------------------------------------------------------- */
     /*      Handle CREATE INDEX statements specially.                       */
     /* -------------------------------------------------------------------- */
diff --git a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
index 0a9c9f3ea6fa..cb0360b541fa 100644
--- a/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
+++ b/ogr/ogrsf_frmts/gpkg/ogrgeopackagedatasource.cpp
@@ -7310,11 +7310,12 @@ OGRLayer *GDALGeoPackageDataset::ExecuteSQL(const char *pszSQLCommand,
         return nullptr;
     }
 
-    if (pszDialect != nullptr && EQUAL(pszDialect, "OGRSQL"))
-        return GDALDataset::ExecuteSQL(osSQLCommand, poSpatialFilter,
-                                       pszDialect);
     else if (pszDialect != nullptr && EQUAL(pszDialect, "INDIRECT_SQLITE"))
         return GDALDataset::ExecuteSQL(osSQLCommand, poSpatialFilter, "SQLITE");
+    else if (pszDialect != nullptr && !EQUAL(pszDialect, "") &&
+             !EQUAL(pszDialect, "NATIVE") && !EQUAL(pszDialect, "SQLITE"))
+        return GDALDataset::ExecuteSQL(osSQLCommand, poSpatialFilter,
+                                       pszDialect);
 
 #if SQLITE_VERSION_NUMBER < 3007017
     // Emulate PRAGMA application_id
diff --git a/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp b/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
index e845a9b6b8e5..8426d2cd885e 100644
--- a/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
+++ b/ogr/ogrsf_frmts/sqlite/ogrsqlitedatasource.cpp
@@ -3206,12 +3206,14 @@ OGRLayer *OGRSQLiteDataSource::ExecuteSQL(const char *pszSQLCommand,
         }
     }
 
-    if (pszDialect != nullptr && EQUAL(pszDialect, "OGRSQL"))
-        return GDALDataset::ExecuteSQL(pszSQLCommand, poSpatialFilter,
-                                       pszDialect);
-    else if (pszDialect != nullptr && EQUAL(pszDialect, "INDIRECT_SQLITE"))
+    if (pszDialect != nullptr && EQUAL(pszDialect, "INDIRECT_SQLITE"))
         return GDALDataset::ExecuteSQL(pszSQLCommand, poSpatialFilter,
                                        "SQLITE");
+    else if (pszDialect != nullptr && !EQUAL(pszDialect, "") &&
+             !EQUAL(pszDialect, "NATIVE") && !EQUAL(pszDialect, "SQLITE"))
+
+        return GDALDataset::ExecuteSQL(pszSQLCommand, poSpatialFilter,
+                                       pszDialect);
 
     /* -------------------------------------------------------------------- */
     /*      Special case DELLAYER: command.                                 */