Aptychodon (meaning "unwrinkled tooth") is an extinct genus of plesiosaur from the Late Cretaceous of the Czech Republic.

[1] The holotype consists of incompletely preserved teeth and they were discovered at White Mountain near Prague, Czech Republic.

[2][3] They were then sent to the Prague Museum before von Reuss (1855) described the teeth and created the species Aptychodon cretaceius.

[3] Aptychodon has been classified as a potential synonym of Polyptychodon interruptus by later authors.

[1] Most authors classify Aptychodon within a basal position in Plesiosauria.