Langilangi Haupeakui (born 3 July 1989) is a United States international rugby union player. His regular playing position is either No. 8 or Flanker. Haupeakui was born in San Mateo, California and played American football before playing rugby union at college. He played with Folau Niua at East Palo Alto Razorbacks before being picked up by Sacramento Express for the inaugural PRO Rugby league in the United States. It was announced on 28 September 2016 that Haupeakui signed for Glasgow Warriors on a two-year deal, subject to visa and medical.