The Sultanah Bahiyah Highway (Malay: Lebuhraya Sultanah Bahiyah), Federal Route 255 (formerly Alor Setar Bypass and Jalan Sultanah, both Kedah State Route K139) is a major highway bypass in Alor Star, Kedah, Malaysia. It was named after the late Sultanah Bahiyah, a first consort of Sultan Abdul Halim of Kedah. The Kilometre Zero is located at Alor Setar North.