| Named By: | P. D. Gingerich in 2007 |
| Time Period: | Late Eocene |
| Location: | Egypt - Birket Qarun Formation, Daba'a Formation, Gehannam Formation |
| Size: | Very roughly estimated about 10 meters long |
| Diet: | Carnivore/Piscivore |
| Fossil(s): | Partial skull and vertebrae |
| Classification: | | Chordata | Mammalia | Cetacea | Archaeoceti | Basilosauridae | |
Masracetus (from Arabic Masr, "Egypt", and Greek ketos, "whale") is an extinct genus of basilosaurid ancient whale known from the Late Eocene (Priabonian, 37.2 to 33.9 million years ago) of Egypt.
Masracetus was briefly described in an addendum by Gingerich 2007 and is known from just an assemblage of vertebrae and a poorly reconstructed skull from 1908. The lumbar vertebrae are large but relatively short (anteroposteriorly) compared to those of other archaeocetes; the diameter is almost the same as for Basilosaurus isis but the length is less than half of the latter. Masracetus is larger than Cynthiacetus.
The species name honours Richard Markgraf, palaeontologist Ernst Stromer's fossil collector, who collected the type specimen in 1905.
Masracetus' type locality is the Birket Qarun Formation in Dime (29.5degN 30.7degE / 29.5; 30.7, paleocoordinates 24.9degN 26.6degE / 24.9; 26.6) north of lake Birket Qarun, but specimens have also been found in the Qattara Depression and Fayum.