The nine dots puzzle is a mathematical puzzle whose task is to connect nine squarely arranged points with a pen by four (or fewer) straight lines without lifting the pen or retracing any lines.

The puzzle has appeared under various other names over the years.

In 1867, in the French chess journal Le Sphinx, an intellectual precursor to the nine dots puzzle appeared credited to Sam Loyd. Loyd's puzzle asked for a sequence of 14 moves of a chess queen passing through all the squares of a chessboard and returning to the starting square; this can be considered as a "64 dots puzzle" of covering all dots of an 8-by-8 square lattice with a closed polygonal path whose segments are horizontal, vertical, or diagonal, and that turns only at the dots.

In 1907, the nine dots puzzle itself appeared, in an interview with Sam Loyd in The Strand Magazine:

In the same year, the puzzle also appeared in a puzzle book by A. Cyril Pearson. It was there named a charming puzzle and involved nine dots.

Both versions of the puzzle thereafter appeared in newspapers. From at least 1908, Loyd's egg-version ran as advertising for Elgin Creamery Co in Washington, DC., renamed to The Elgin Creamery Egg Puzzle. From at least 1910, Pearson's "nine dots"-version appeared in puzzle sections.

In 1914, Sam Loyd's Cyclopedia of Puzzles was published posthumously by his son (also named Sam Loyd). The puzzle is therein explained as follows:

Sam Loyd's naming of the puzzle is an allusion to the story of Egg of Columbus.