An octomino is an 8-polyomino. There are 369 free (illustrated above), 704 one-sided, and 2725 fixed octominoes.
Octomino
See also
PolyominoExplore with Wolfram|Alpha
References
Keller, M. "The Octominoes." http://members.aol.com/wgreview/octomino.html.Referenced on Wolfram|Alpha
OctominoCite this as:
Weisstein, Eric W. "Octomino." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Octomino.html