This is a list of puzzles that cannot be solved. An impossible puzzle is a puzzle that cannot be resolved, either due to lack of sufficient information, or any number of logical impossibilities.
15 Puzzle – Slide fifteen numbered tiles into numerical order. It is impossible to solve in half of the starting positions.[1]
Five room puzzle – Cross each wall of a diagram exactly once with a continuous line.[2]
MU puzzle – Transform the string MI to MU according to a set of rules.[3]
Three cups problem – Turn three cups right-side up after starting with one wrong and turning two at a time.[8]
Three utilities problem – Connect three cottages to gas, water, and electricity without crossing lines.[9]
Thirty-six officers problem – Arrange six regiments consisting of six officers each of different ranks in a 6 × 6 square so that no rank or regiment is repeated in any row or column.[10]
^Holton, Derek Allan; Sheehan, J. (1993). The Petersen graph. Australian Mathematical Society lecture series. Cambridge [England]: Cambridge University Press. ISBN978-0-521-43594-9.