How early in a game can stalemate occur?
In a real game (Sibilio - Mariotti, Ravenna 1982) it happend after black's 27th move. I don't know if this is the shortest or not.
In 'constructed games' it can go faster. The lowest number I have seen is 10.
But really nice is this game where stalemate in 12 moves is achieved without anything being captured on the board.
Source: Gameknot forum.