diff --git a/Mk/bsd.default-versions.mk b/Mk/bsd.default-versions.mk
index 2a02ff95704f0..5780cfe7c374d 100644
--- a/Mk/bsd.default-versions.mk
+++ b/Mk/bsd.default-versions.mk
@@ -125,7 +125,7 @@ _EXPORTED_VARS+=	_PERL5_FROM_BIN
 PERL5_DEFAULT:=		${_PERL5_FROM_BIN:R}
 .  endif
 # Possible values: 11, 12, 13, 14, 15
-PGSQL_DEFAULT?=		13
+PGSQL_DEFAULT?=		15
 # Possible values: 8.0, 8.1, 8.2, 8.3
 PHP_DEFAULT?=		8.1
 # Possible values: rust, legacy
diff --git a/UPDATING b/UPDATING
index 20f526787b7f9..154adaceb34a4 100644
--- a/UPDATING
+++ b/UPDATING
@@ -5,6 +5,62 @@ they are unavoidable.
 You should get into the habit of checking this file for changes each time
 you update your ports collection, before attempting any port upgrades.
 
+20230908:
+  AFFECTS: users of databases/postgresql* and other software using PostgreSQL to run
+  AUTHOR: kbowling@FreeBSD.org
+
+  The default version of PostgreSQL has been switched from 13 to 15.
+  The upgrade procedure can use up twice the space the databases
+  currently needs. If you have a big amount of stored data take a
+  closer look at the manpage of pg_upgrade for avoidance and/or
+  speedup of the upgrade.
+
+  The upgrade instructions consider a basic usage and do not match
+  complex scenarios like replication, sharding, or similar.
+
+  Upgrade instructions:
+
+  First stop your PostgreSQL, create PostgreSQL-binaries and backup your data.
+  If you have another Version of PostgreSQL installed, for example 13, your
+  files are named according to this.
+
+  # service postgresql stop
+  # pkg create postgresql13-server postgresql13-contrib
+  # mkdir /tmp/pg-upgrade
+  # tar xf postgresql13-server-13.12.pkg -C /tmp/pg-upgrade
+  # tar xf postgresql13-contrib-13.12.pkg -C /tmp/pg-upgrade
+  # pkg delete -f databases/postgresql13-server databases/postgresql13-contrib databases/postgresql13-client
+
+  Now update PostgreSQL:
+
+    pkg user:
+    # pkg install databases/postgresql15-server databases/postgresql15-contrib
+    # pkg upgrade
+
+    Portmaster users:
+    # portmaster databases/postgresql15-server databases/postgresql15-contrib
+    # portmaster -a
+
+    Portupgrade users:
+    # portinstall databases/postgresql15-server databases/postgresql15-contrib
+    # portupgrade -a
+
+  After installing the new PostgreSQL version you need to convert
+  all your databases to new version:
+
+  # su -l postgres -c "/usr/local/bin/initdb --encoding=utf-8 --lc-collate=C -D /var/db/postgres/data15 -U postgres"
+  # su -l postgres -c "pg_upgrade -b /tmp/pg-upgrade/usr/local/bin/ -d /var/db/postgres/data13/ -B /usr/local/bin/ -D /var/db/postgres/data15/ -U postgres "
+
+  Now the migration is finished. You can start PostgreSQL again with:
+
+  # service postgresql start
+
+  ATTENTION:
+  1) The default user changed from "pgsql" to "postgres" in 11. The migration steps above now assume
+     the "postgres" database user and FreeBSD user.
+  2) See the updating entry 20190829 if you are updating from a release prior to 11.
+  3) If you use non-default initdb options, you have to adjust the initdb-command accordingly
+
 20230906:
   AUTHOR: jrm@FreeBSD.org
   AFFECTS: users of sysutils/devcpu-data*