Rhesus may refer to:
- Rhesus of Thrace, a king in Greek mythology
- S. Vivianus Rhesus, a Roman governor of Thrace
- In Greek mythology, a river-god, son of Oceanus and Tethys
- Rhesus (play), the Ancient Greek tragedy thought to have been written by Euripides
- rhesus macaque, also known as the rhesus monkey
- Rhesus factor, associated with a blood type, named for the monkey
- Rh disease, also known as Rhesus disease
- 9142 Rhesus, an asteroid
- Rhesus Glacier