This paper reports the presence of two new species of
Marphysa from São Sebastião Channel, State of São Paulo, Brazil,
M. sebastiana n. sp. and
M. formosa n. sp., both collected from intertidal sandy beaches. These species belong to the group of
Marphysa that has branchiae scattered over an extensive region of the body and parapodia with both compound falcigerous and spinigerous chaetae. Comparisons between the two new species and
M. digitibranchia Hoagland, 1920,
M. orensanzi Carrera-Parra and Salazar-Vallejo, 1998,
Marphysa sp. B (Gardiner, 1975), and
Marphysa sp. (Winsnes, 1989) are presented.