Stack-Up is a video game released in 1985 for the Nintendo Entertainment System, designed for use with the Robotic Operating Buddy (R.O.B.) Stack-Up is one of two games in Nintendo's Robot Series, the other being Gyromite (Robot Gyro in Japan). While Gyromite is a pack-in game with the R.O.B. itself and therefore comes with all the parts needed to play the game, Stack-Up comes in a large box containing additional bases and colored discs. The game's retail box comes with many small, plastic parts, which may contribute to difficulty in maintaining a complete set. Stack-Up is considered by collectors to be one of the rarest first-party games for the NES.

In some modes, Professor Hector works with R.O.B. to organize blocks. In others, Hector competes for control of R.O.B. against "glitches" named Spike & Flipper, or against Professor Vector.