State Route 378 (SR 378) is a short, four-lane highway that runs west-to-east for about 6.4 miles (10.3 km) entirely in Gwinnett County in the north-central part of the U.S. state of Georgia.

From its western terminus at US 23/SR 13 in Norcross, it runs east, crossing over Interstate 85 (I-85) before coming to its eastern terminus at US 29/SR 8 in Lilburn. The route is heavily commercialized with numerous office and industrial parks. It is known along its entire length as Beaver Ruin Road.

The entire route is in Gwinnett County.