Arcestes is a genus of extinct ceratitid ammonites found in Triassic-aged marine strata.

Unlike many other ammonites, the shells of Arcestes lack keels that would otherwise stabilize them while swimming.

Lateral lobes and saddles have generally triangular outlines but are deeply embayed by strong projections forming tree-like patterns.

They form a series diminishing in size and complexity in a rather straight line going from the venter to the umbilicus in the middle of the shell.

Fossils of Arcestes are found in Mid to Upper Triassic marine strata throughout the world, including California (A. pacificus), Nevada (A (Anisarcestes) mrazici) and Austria (A. intuslabiatus and A.