Peterjohnsiidae is a small family of millipedes belonging to the order Chordeumatida.

[1] The family was first described in 1987 by Jean-Paul Mauriès.

[2][3] These millipedes range from 3 mm to 8 mm in length and are found in Australia.

[4] Species in this family exhibit sexual dimorphism in segment number: adult males have 30 segments, but adult females have 32 segments (counting the collum as the first segment and the telson as the last).

[5][3] In adult males in this family, the gonopod complex involves three leg pairs (pairs 8 through 10) rather than just the two (pairs 8 and 9) usually modified into gonopods in this order.