Williamsoniaceae is a family within the Bennettitales, an extinct group of seed plants.

Members of this family are believed to have been around two meters tall and with widely serrate leaves along a central stem.

Reproductive organs of the Williamsoniaceae have varied widely in the fossil record but almost all have been found to be borne on stalks emerging from a ring of leaves.

[1] This family is different from Cycadeoidaceae by having the presence of cones leaving the major axis and lateral branches associated with a long peduncle covered by bracts.

Some of this family reproduce by sporangia and others only produce ovule or pollen sacs.