Justin Lui (born 8 May 2000) is a Canadian volleyball player. He is a member of the Canada men's national volleyball team and a participant in 2024 Summer Olympics.
Lui competed for the Stanford University men's volleyball team while in university, from 2018 to 2023. In 2020, he trained with the Volleyball Canada National Excellence Program in Gatineau.
He signed for Finnish professional volleyball club Vantaa Ducks in 2023, playing with them for the 2023-2024 season. In 2024, he signed for Czech club VK Dukla Liberec.
Lui has competed for Canada at the FIVB Men's Volleyball Nations League during the 2022, 2023 and 2024 seasons. In July 2024, Lui was named to Canada's 2024 Olympic team.
In 2020, Lui came out as gay by writing an email to his university volleyball team.