五格骨牌（Pentomino），又称五连块、伤脑筋十二块，是一种多格骨牌，每块以五个全等的正方形连成，反射或旋转视作同一种共有十二种，可以英文本母代表。其谜题，最早是英国人亨利·杜德耐于1907年所发明，书名《坎特伯雷趣题和其他奇特问题》（Canterbury Puzzles and Other Curious Problems）。

改用全等的立方体组合，就可以以此砌成立体。

A pentomino is a plane geometric figure formed by joining five equal squares edge to edge. It is a polyomino with five cells. There are twelve pentominoes, not counting rotations and reflections as distinct. They are used chiefly in recreational mathematics for puzzles and problems. Pentominoes were formally defined by American professor Solomon W. Golomb starting in 1953 and later in his 1965 book Polyominoes: Puzzles, Patterns, Problems, and Packings. Golomb coined the term "pentomino" from the Ancient Greek πέντε / pénte, "five", and the -omino of domino, fancifully interpreting the "d-" of "domino" as if it were a form of the Greek prefix "di-" (two). Golomb named the 12 free pentominoes after letters of the Latin alphabet that they resemble.