It's Mr. Pants is a puzzle video game developed by Rare. It was published by THQ for the Game Boy Advance (GBA) handheld game console in North America and Europe in 2004–2005. A port of the game for mobile phones was developed and published internationally by In-Fusio in 2005–2006. The game stars Mr. Pants, a crudely drawn mascot formerly featured on Rare's website who had made cameo appearances in several prior Rare games.

The basic idea of the game is to create rectangles which have to be two-by-three blocks or larger to clear them from the grid. Blocks cannot be placed on top of blocks of the same color that are already on the grid, but they can be placed on top of blocks of any other color which causes the different blocks on the grid to disappear.

The game incorporates three main game modes: Puzzle, in which players must clear a puzzle board using a limited selection of specific blocks; Wipeout, in which players have a two minute time limit to clear all blocks from the grid; and Marathon, in which the available grid space is slowly restricted while players attempt to achieve the highest score possible. Each mode has four difficulty levels, ranging from "Easy" to "Special", with each difficulty unlocked after clearing the previous one. Players are awarded a trophy for each successfully completed difficulty level. Upon completing all four difficulties in Puzzle mode, a fourth game type is unlocked called "Max the Mystical Mouse's Muddle", in which players must clear rectangles of specific sizes as provided by the eponymous Max.