Mexichromis macropus is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Chromodorididae.

[2] This species is recorded from temperate and subtropical Australia including SW Western Australia, South Australia, Tasmania, Victoria, New South Wales and southern Queensland.

[3] Mexichromis macropus has a mantle border decorated with radially arranged orange or yellow-orange stripes rather than spots, as in Mexichromis katalexis or continuous lines as in Mexichromis mariei.

The mantle ranges in colour from white to pink-purple and has scattered pointed papillae tipped in purple.

[3] This species feeds on a sponge in the genus Dysidea.