Blockout is a puzzle video game, published in 1989 by California Dreams, developed in Poland by Aleksander Ustaszewski and Mirosław Zabłocki.

The game is the logical extension of Tetris into the third dimension. In regular Tetris, the player manipulates a set of tetrominoes which fall into a two-dimensional pit (seen from the side). The aim is to solve a real-time packing problem by forming complete rows, which then disappear and score points. Poor play leads to incomplete rows, caused by inefficient arrangements of tiles; these rows do not disappear, giving the player progressively less space and less time to play subsequent pieces. Similarly, in Blockout, the player manipulates a set of polycubes which fall into a three-dimensional pit (seen from above; the pieces appear in the foreground and fall away). The pieces can be rotated around all three axes, and moved horizontally and vertically. The aim is to form complete layers.