user34197: This is to complement the kingside variant of that question
Has checkmate ever been achieved by a castling queen side in a high-level game?

user34197: According to that CQL query :
cql(input Megabase2023.pgn)

mate
move previous from [Kk] o-o-o


15 games had queen side castle deliver checkmate, including 5 by 2000+ players

[Title "Vlassov, Nikolai (2466) v. Wirig, Anthony (2422) - EU-ch Internet qual (2003, blitz) - Playchess.com"]
[FEN ""]

1.e4 c6 2.d4 d5 3.e5 Bf5 4.Nc3 Qb6 5.Nf3 e6 6.Bd3 Bxd3 7.
Qxd3 Qa6 8.Qxa6 Nxa6 9.a3 c5 10.Be3 h6 11.Nb5 Kd7 12.dxc5 Nxc5 13.b4 a6 14.Nc3
Ne4 15.Nxe4 dxe4 16.Nd2 a5 17.Nc4 Kc6 18.Nxa5+ Kd5 19.Bf4 g5 20.O-O-O#


[Title "Heimisson, Hilmir Freyr (2394) v. Fossan, Andreas (2025) - Nordic-ch U20 (2019)"]
[FEN ""]

1.e4 c6 2.Nc3 d5 3.Qf3 d4 4.Bc4 e6 5.Nce2 Ne7 6.Qg3 a5 7.
a3 b5 8.Ba2 Bb7 9.d3 Ng6 10.h4 Bd6 11.f4 Rg8 12.Nf3 Na6 13.h5 Ne7 14.Nexd4 Nc7
15.Be3 c5 16.Ne2 Nc6 17.Qf2 Na6 18.h6 Qc7 19.e5 Be7 20.Nc3 Qb6 21.f5 exf5 22.
Bxf7+ Kxf7 23.Ng5+ Bxg5 24.Qxf5+ Bf6 25.exf6 gxf6 26.Qxh7+ Ke6 27.Nd5 Kxd5 28.
Qf7+ Ke5 29.Rh5+ Rg5 30.Bf4+ Kxf4 31.Qxf6+ Kg3 32.Rh3+ Kxg2 33.Qf3+ Kg1 34.
O-O-O#


[Title "Garcia, Alvaro (2231) v. Gonzalez Parejo, Ramon Junior (2067) - COL-ch sf Medellin (2019)"]
[FEN ""]

1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nge2 c5 6.d5 O-O 7.
Ng3 Bg4 8.f3 Bd7 9.h4 Na6 10.h5 Nc7 11.Bf4 a6 12.Qd2 b5 13.Bh6 bxc4 14.Bxg7
Kxg7 15.hxg6 fxg6 16.Qh6+ Kg8 17.Bxc4 Nb5 18.e5 dxe5 19.Nge4 Rf7 20.Nxf6+ exf6
21.d6 Nxd6 22.Qxh7+ Kf8 23.Qh8+ Ke7 24.Nd5+ Ke6 25.Nf4+ Kf5 26.g4+ Kxf4 27.Qh2+
Ke3 28.Qd2+ Kxf3 29.Rh3+ Kxg4 30.Qg2+ Kf4 31.Rf3+ Ke4 32.Qe2+ Kd4 33.O-O-O#


[Title "Van Riemsdijk, Dirk Dagobert (2137) v. Queiroz, Stella Becker - Santos Paulista-ch (2011)"]
[FEN ""]

1.e4 c6 2.Nc3 d5 3.Qf3 d4 4.Bc4 dxc3 5.Qxf7+ Kd7 6.dxc3
b5 7.Bf4 bxc4 8.O-O-O#


[Title "Kablar, Dorian (1538) v. Hilby, Craig (2420) - Kasparov CF University Cup (Lichessm rapid, 2022)"]
[FEN ""]

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Nc3 Nf6 5.d3 d6 6.Bg5 h6 7.
Bh4 a6 8.O-O g5 9.Bg3 Na5 10.Bb3 Nxb3 11.axb3 h5 12.h3 h4 13.Bh2 g4 14.hxg4
Bxg4 15.Qd2 h3 16.Bg3 Nh5 17.Kh2 hxg2 18.Kxg2 Bh3+ 19.Kxh3 Nf4+ 20.Kg4 Qd7+ 21.
Kg5 Nh3+ 22.Kf6 Qe6+ 23.Kg7 Qg6+ 24.Kxh8 O-O-O#


34197: <p><em>This is to complement the <a href="https://chess.stackexchange.com/q/41659/34197">kingside</a> variant of that question</em></p>
<p>Has checkmate ever been achieved by a castling queen side in a high-level game?</p>
 34197: <p>According to that <a href="http://gadycosteff.com/cql" rel="nofollow noreferrer">CQL</a> query :</p>
<pre><code>cql(input Megabase2023.pgn)

mate
move previous from [Kk] o-o-o
</code></pre>
<hr />
<p><a href="https://gist.github.com/signed-log/f8e2064411a514859148583d815e7283" rel="nofollow noreferrer">15 games</a> had queen side castle deliver checkmate, including 5 by 2000+ players</p>
<hr />
<pre><code>[Title &quot;Vlassov, Nikolai (2466) v. Wirig, Anthony (2422) - EU-ch Internet qual (2003, blitz) - Playchess.com&quot;]
[FEN &quot;&quot;]

1.e4 c6 2.d4 d5 3.e5 Bf5 4.Nc3 Qb6 5.Nf3 e6 6.Bd3 Bxd3 7.
Qxd3 Qa6 8.Qxa6 Nxa6 9.a3 c5 10.Be3 h6 11.Nb5 Kd7 12.dxc5 Nxc5 13.b4 a6 14.Nc3
Ne4 15.Nxe4 dxe4 16.Nd2 a5 17.Nc4 Kc6 18.Nxa5+ Kd5 19.Bf4 g5 20.O-O-O#
</code></pre>
<hr />
<pre><code>[Title &quot;Heimisson, Hilmir Freyr (2394) v. Fossan, Andreas (2025) - Nordic-ch U20 (2019)&quot;]
[FEN &quot;&quot;]

1.e4 c6 2.Nc3 d5 3.Qf3 d4 4.Bc4 e6 5.Nce2 Ne7 6.Qg3 a5 7.
a3 b5 8.Ba2 Bb7 9.d3 Ng6 10.h4 Bd6 11.f4 Rg8 12.Nf3 Na6 13.h5 Ne7 14.Nexd4 Nc7
15.Be3 c5 16.Ne2 Nc6 17.Qf2 Na6 18.h6 Qc7 19.e5 Be7 20.Nc3 Qb6 21.f5 exf5 22.
Bxf7+ Kxf7 23.Ng5+ Bxg5 24.Qxf5+ Bf6 25.exf6 gxf6 26.Qxh7+ Ke6 27.Nd5 Kxd5 28.
Qf7+ Ke5 29.Rh5+ Rg5 30.Bf4+ Kxf4 31.Qxf6+ Kg3 32.Rh3+ Kxg2 33.Qf3+ Kg1 34.
O-O-O#
</code></pre>
<hr />
<pre><code>[Title &quot;Garcia, Alvaro (2231) v. Gonzalez Parejo, Ramon Junior (2067) - COL-ch sf Medellin (2019)&quot;]
[FEN &quot;&quot;]

1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nge2 c5 6.d5 O-O 7.
Ng3 Bg4 8.f3 Bd7 9.h4 Na6 10.h5 Nc7 11.Bf4 a6 12.Qd2 b5 13.Bh6 bxc4 14.Bxg7
Kxg7 15.hxg6 fxg6 16.Qh6+ Kg8 17.Bxc4 Nb5 18.e5 dxe5 19.Nge4 Rf7 20.Nxf6+ exf6
21.d6 Nxd6 22.Qxh7+ Kf8 23.Qh8+ Ke7 24.Nd5+ Ke6 25.Nf4+ Kf5 26.g4+ Kxf4 27.Qh2+
Ke3 28.Qd2+ Kxf3 29.Rh3+ Kxg4 30.Qg2+ Kf4 31.Rf3+ Ke4 32.Qe2+ Kd4 33.O-O-O#
</code></pre>
<hr />
<pre><code>[Title &quot;Van Riemsdijk, Dirk Dagobert (2137) v. Queiroz, Stella Becker - Santos Paulista-ch (2011)&quot;]
[FEN &quot;&quot;]

1.e4 c6 2.Nc3 d5 3.Qf3 d4 4.Bc4 dxc3 5.Qxf7+ Kd7 6.dxc3
b5 7.Bf4 bxc4 8.O-O-O#
</code></pre>
<hr />
<pre><code>[Title &quot;Kablar, Dorian (1538) v. Hilby, Craig (2420) - Kasparov CF University Cup (Lichessm rapid, 2022)&quot;]
[FEN &quot;&quot;]

1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Nc3 Nf6 5.d3 d6 6.Bg5 h6 7.
Bh4 a6 8.O-O g5 9.Bg3 Na5 10.Bb3 Nxb3 11.axb3 h5 12.h3 h4 13.Bh2 g4 14.hxg4
Bxg4 15.Qd2 h3 16.Bg3 Nh5 17.Kh2 hxg2 18.Kxg2 Bh3+ 19.Kxh3 Nf4+ 20.Kg4 Qd7+ 21.
Kg5 Nh3+ 22.Kf6 Qe6+ 23.Kg7 Qg6+ 24.Kxh8 O-O-O#
</code></pre>
