The Opera Game is a famous chess game played in 1858 between an American Paul Morphy and a German and French aristocrat (Karl, Duke of Brunswick and Count Isouard), playing together.
The Frenchmen invited Morphy to the Paris Opera, then asking him to join them in a chess game. The Duke and the Count (playing black) were allowed to consult each other during play.
The game has been much reproduced in the years since it was played and is often used by chess teachers to demonstrate the importance of rapidly developing one's pieces. It is given here in algebraic notation.
1. e4 e5 2. Nf3 d6
This is Philidor's Defense.
3. d4 Bg4
3...exd4 is more normal. 3...f5 is a more aggressive alternative.
4. dxe5 Bxf3
If ... dxe5, then 5. Qxd8 Kxd8 and Black has lost the right to castle.
5. Qxf3 dxe5 6. Bc4 Nf6 7. Qb3 Qe7 8. Nc3
White prefers fast development to material.
8. ... c6 9. Bg5 b5 10. Nxb5!
Morphy chooses not to retreat the bishop, which would allow Black to gain time for development.
10. ... cxb5 11. Bxb5+ Nbd7 12. 0-0-0
The combination of the bishop's pin on the knight and the open file for the rook will lead to Black's defeat.
12. ... Rd8 13. Rxd7 Rxd7 14. Rd1 Qe6
Compare the activity of the White pieces with the idleness of the Black pieces.
15. Bxd7+ Nxd7
If ... Qxd7, then 16. Qb8+ Ke7 17. Qxe5+ Kd8 18. Bxf6+ gxf6 19. Qxf6+ Kc8 20. Rxd7 Kxd7 21. Qxh8 and White is clearly winning.
16. Qb8+! Nxb8 17. Rd8#
The game in PGN format (see Portable Game Notation)