Yes, there has been a stalemate in a serious game that is under 30 moves long. According to Tim Krabbe's "Chess Records," the fastest such game happened in 27 moves.
[Title "Sibilio-Mariotti, Ravenna, 1982"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1. e4 e6 2. Nf3 d5 3. e5 c5 4. b4 cxb4 5. d4 Nh6 6. a3 ...
Sam Loyd, a famous puzzle composer, created this 10 move, 19 ply, stalemate game over 100 years ago. I found it via Google, in this post by AndersElborg on chess.com. Most black pieces are blocked, which saves some moves because those pieces don't need to be captured.
1.e3 a5 2.Qh5 Ra6 3.Qxa5 h5 4.h4 Rah6 5.Qxc7 f6 6.Qxd7+ Kf7 7....
Assuming you allow promoted material (since you didn't say anything :-),
this (on Page 13 of the PDF) is the (unfortunately, extremely unknown) finite record since ages. It shows the record for the longest sequence of only 1 legal move for each side, with use of promoted material.
[Title "Karl Scherer, Feenshach 1980, Page 13"]
[FEN "1B1Q1Q2/2R5/pQ4QN/RB2k3/1Q5Q/N4Q2/K2Q4/6Q1 w - - 0 1 "]
105 mates — Nenad Petrovic, Sahovski Vjesnika 1947 (Chess Problem Database)
In this position any check is mate. There are 3 knight mates (c4, g4, f7), 23 discovered mates (14 moves for the rook on c7, 9 for the bishop on b5), and 79 queen mates: 1 on a1, 2 on b2, 3 on c3, 4 on c5, 6 on d4, 3 on ...
Anthony Stewart Mackay Dickens found another solution, also with 105 mating moves, but with only 17 units in the diagram (16 white and the black king):
[title "Anthony Stewart Mackay Dickens, The Problemist, Jan 1970. 105 mates"]
[fen "2Q1Q3/2Q4Q/Q4Q2/3k4/Q5Q1/1R6/B1NBQ3/K2R1N2 w - - 0 1"]
This may be found here on PDB.
Black's last move must have been ......
Sir Jeremy Morse, in Chess Problems: Tasks and Records, Introduction, cites this construction by E. Luukonen:
[Title "E. Luukonen, Uusi Suomi, 1936"]
[fen "kr6/pnPPPPPPPP/P2N4/R7/3BBN2/1Q6/3K3P/6R1 w - - 0 1"]
All of White's 117 moves lead to mate in 2. White has no mate in 1, but if Black's rook were to move, or if (after White captures ...
the shortest known mate by en passant capture is in 5.5 moves
(that is, White mates on move 6), and was published by Benko in
Chess Live & Review in 1976:
[Title "Pal Benko's 5.5 move e.p. helpmate"]
[Fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 0"]
1. e4 e5 2. Qh5 Nc6 3. g4 d6 4. g5 Kd7 5. Bh3+ f5 6. gxf6#
On move 3, Black can crash through with his queen on f2 or d2 via several different squares, forcing White to respond. There is no series of White moves that can prevent all such checks.
1. Nf3 (1. e3 e5 2. c3 Qf6 3. g3 Qxf2+) 1... c6 (1... e5 2. c3 Qh4 3. e3 Qxf2+) 2. g3 Qa5 (2... Qb6 3. c3 Qxf2+) 3. e3 Qxd2+ *
The same question has also been discussed and answered in the lichess forum, and as mentioned by others already, the answer is 11 half-moves for white and 12 half-moves for black. You might find some interesting examples and additional info there. Not knowing that this problem had already been solved before, I did a brute-force proof back then (see my post ...
In other words, you wish for the record length for a completely dual-free sequence. Every White move must be absolutely unique to any possible by Black. Shorter, dualed mating sequences do not count.
To that end, I remembered a mate in 61 from this page on SuperProblem.ru (a Russian based chess problem site). It is also in the Die Schwalbe Chess Problem ...
After some searching, it seems that this composition is the current record holder. 218 moves; legal position with promotions:
R6R/3Q4/1Q4Q1/4Q3/2Q4Q/Q4Q2/pp1Q4/kBNN1KB1 w - - 0 1
Another version of the position (same number of moves):
3Q4/1Q4Q1/4Q3/2Q4R/Q4Q2/3Q4/1Q4Rp/1K1BBNNk w - - 0 1
79 moves (for black); from actual game between Davis and ...
Otto Blathy is famous for his long mate problems. There are different records depending on whether you allow an illegal starting position, or promoted pieces, or minor duals in the solution, so your answer might be anywhere between 257 and 292 moves.
This answer on Puzzling.SE shows a construction in 271 moves that is not Blathy, but by Nenad Petrovic.
This sounds like a job for Tim Krabbé, who presents two games with six queens: Szalanczy - Nguyen, Budapest 2009 and Anton - Franco, XXI Elgoibar Magistral 2011. I don't know how many of the participants were grandmasters.
There are some other games with 5+ queens at Chess Siberia. Of these, Miton - Benjamin, World Open Philadelphia 2005 definitely features ...
Longest known checkmate is in 549 moves, revealed by Lomonosov Tablebases.
You can see the game here.
Plus, you don't need to say "endgame" explicitly. Longest checkmates come from endgame tablebases already. And it's not possible to build a middlegame tablebase practically, because of the exponential space complexity. Let's say there is a middlegame ...
The raw data which could be used to extract this information is available on the FIDE website (from 2001) and the Olimpbase website (before 2001). What you will need to do is clean the data (the older the data the more "dirty" it is), construct a relational database and insert the data. Then you will be able to use SQL to search the database for ...
Some cleaning up is required, I think:
The number on the website you link to differs from the results published in Bonsdorff et al., Schach und Zahl. Unterhaltsame Schachmathematik. pp. 11–13.
There they say that if the 50-move-rule is mandatory the longest possible game (i.e. where both players cooperate to achieve the weird goal of a game of maximal ...
This is a famous task, originally tackled by Sam Loyd and only improved a century later. See http://www.chessvariants.com/problems.dir/twokingstask.html, which gives the refinement by Ponzetto:
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1.e4 d5 2.exd5 Qxd5 3.Bd3 Qxa2 4.Bxh7 Qxb1 5.Bxg8 Qxc2 6.Bxf7+ Kxf7 7.Rxa7 Qxc1 8.Rxb7 Rxh2 9.Rxb8 ...
I've come up with 23, in the following position, with promotions:
[FEN "nb2k3/2p5/1pP5/1Pp5/2P1p1p1/3pPpPp/3P1P1B/4KNBN w - - 0 1"]
Funny task. I think I'm still pretty far from the maximum, but here is a suggestion with
[title "Challenge 3, 23 units"]
[FEN "NRN1k1bn/QRKpPp2/PPpP1Pp1/2P3Pp/7P/8/7B/8 w - - 0 1"]
With black to move, an almost-dishonest trick to reach 25:
[title "Challenge 3, BTM, 25 units"]
[FEN "BRN1Nkbn/QRKpPp2/PPpP1Pp1/2P3Pp/7P/8/1r6/B7 b - - 0 ...
There are Several reasons for identical games:
The fact that we databases and computers allows us to find the best move in known positions. (if both players knows the theory in the same level - it might lead to a known draw).
Hence some players might follow a known game between two great players, which might result with identical games.
The fact that ...
You mean like this?
[Title "Vilhelm Röpke, Skakbladet 1942, Mate In 6"]
[FEN "K1k5/P1Pp4/1p1P4/8/p7/P2P4/8/8 w - - 0 1"]
White mates in 6.
I guess that's 9 consecutive forced moves. It would be eleven except for black's choice of promotion piece on his fifth move. I don't know if it's a record, and I don't know who composed this classic ...