Cut the Knot is an interactive mathematics website created by Alexander Bogomolny in 1996 to make mathematics accessible and engaging online. It offers a wide-ranging collection of explanations, articles, puzzles, games, visual demonstrations, and interactive activities for learners interested in mathematical ideas and problem-solving. Topics include arithmetic, algebra, geometry, probability, calculus, logic, combinatorics, fractals, and mathematical fallacies, alongside practical resources such as word problems and fast arithmetic tips.

Visitors can explore classic challenges—including the Tower of Hanoi, Monty Hall dilemma, and Three Jugs Problem—and investigate the reasoning behind their solutions. The site also features visual illusions, mathematical curiosities, proofs, analog devices, and material on mathematics in social science. A commemorative book, Cut the Knot, presents selected probability riddles and solutions, inviting readers to attempt each puzzle before consulting the answer.

Following Bogomolny’s death in 2018, his family and friends asked the Wolfram Foundation to steward the site’s continued maintenance and updates. Cut the Knot serves as an extensive, freely browsable resource for curious learners and puzzle enthusiasts