A tridecagon, sometimes also called a triskaidecagon, is a 13-sided polygon.
An example is the hat polykite, illustrated above.
Tridecagon
See also
Polygon, Regular TridecagonExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Tridecagon." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Tridecagon.html