This is a list of puzzles that cannot be solved.

- 15 puzzle – Slide fifteen numbered tiles into numerical order. Impossible for half of the starting positions.
- Five room puzzle – Cross each wall of a diagram exactly once with a continuous line.
- MU puzzle – Transform the string
`MI`to`MU`according to a set of rules. - Mutilated chessboard problem – Place 31 dominoes of size 2×1 on a chessboard with two opposite corners removed.
- Coloring the edges of the Petersen graph with three colors
- Seven Bridges of Königsberg – Walk through a city while crossing seven bridges exactly once.
- Three cups problem – Turn three cups right-side up after starting with one wrong and turning two at a time.
- Three utilities problem – Connect three cottages to gas, water, and electricity without crossing lines.

## See also

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