3D tic-tac-toe, also known by the trade name Qubic, is an abstract strategy board game, generally for two players.

As with traditional tic-tac-toe, several commercial sets of apparatus have been sold for the game, and it may also be played with pencil and paper with a hand-drawn board.

A game board can easily be drawn by hand, with players using the usual "naughts and crosses" to mark their moves.

[1] Gobblets Gobbler[2] and Otrio,[3] use marker sizes (small, medium, large) as the replacement of the third element.

"Qubic" is the brand name of equipment for the 4×4×4 game that was manufactured and marketed by Parker Brothers, starting in 1964.

In the original issue, the bottom level board was opaque plastic, and the upper three clear, all of simple square design.

The circular playing pieces resembled small poker chips in red, blue, and yellow.

The earliest of these used console lights and switches, text terminals, or similar interaction: the human player would enter moves numerically (for example, using "4 2 3" for fourth level, second row, third column) and the program would respond similarly, as graphics displays were uncommon.

A program written for the IBM 650 used front panel switches and lights for the user interface.

It included lookahead to 12 moves and kept a history of previous games with each opponent, modifying its strategy according to their past behavior.

[13] An implementation in Fortran was written by Robert K. Louden and presented, with an extensive description of its design, in his book Programming the IBM 1130 and 1800.

[16][17] The program was written by Carol Shaw, who went on to greater fame as the creator of Activision's River Raid.

[20] Three-dimensional tic-tac-toe on a 4x4x4 board (optionally 3x3x3) was included in the Microsoft Windows Entertainment Pack in the 1990s under the name TicTactics.