Butterworth (population 108,000) is the principal town of Province Wellesley (Malay: Seberang Perai) in the state of Penang in Malaysia. To many locals, Butterworth is known as Bagan. Butterworth is the site of the Malayan Railway station for Penang, and is linked to the island by the Penang Ferry Service and by the 13.5 km Penang Bridge.

A point of tourist interest in the town is the Penang Bird Park, a landscaped park with over 300 species of birds from all over Southeast Asia.

Butterworth is also the site of a Royal Malaysian Air Force station, RMAF Butterworth, formerly operated by the Royal Air Force and the Royal Australian Air Force, and is now the Headquarters of the Integrated Area Defence System (HQIADS) of the Five Power Defence Arrangements.

Butterworth will be the site of an integrated transport hub called Penang Sentral, which will integrate rail, ferry and bus transport.