The Mullica River is a 50.6-mile-long (81.4 km) river in southern New Jersey in the United States. The Mullica was once known as the Little Egg Harbor River.

The river provides one of the principal drainages into the Atlantic Ocean of the extensive Pinelands. Its estuary on Great Bay is considered one of the least-disturbed marine wetlands habitats in the northeastern United States.

It rises in central Camden County, near Berlin, on the southeastern fringes of the New Jersey suburbs of Philadelphia. It flows generally east-southeast across the state, crossing the Wharton State Forest. Near The Forks, where it receives the Batsto River, the Mullica broadens into a navigable river approximately 20 miles (32 km) long, stretching east-southeast and emptying into Great Bay approximately 10 miles (16 km) north of Atlantic City. Approximately 3 miles (5 km) upstream from its mouth on Great Bay it receives the estuary of the Wading River from the north. Approximately 2 miles (3 km) upstream from its mouth it receives the Bass River from the north.