Is pawn promotion obligatory? According to Wikipedia, when a pawn advances to the eighth rank, the pawn is promoted as a part of the move.

However, this doesn't make it clear whether I am obliged to promote the pawn if it gets to the eighth rank.
Yes, it is obligatory.

From FIDE's Laws of Chess §3.7e (Link):


  e. When a player, having the move, plays a pawn to the rank furthest from its starting position, he must exchange that pawn as part of the same move for a new queen, rook, bishop or knight of the same colour on the intended square of arrival.