Alistair William Johnston is a Canadian professional soccer player who plays as a right-back for Scottish Premiership club Celtic and for the Canada national team.

Johnston began his senior career with Vaughan Azzurri. He speaks English and French and comes from a soccer-oriented family—his father, Bill, and brother, Malcolm, are both involved in the sport. His father, Bill, was born in Vancouver, while his mother, Catherine, was born in Newtownards, Northern Ireland. When he was four years old, his family moved from Vancouver to Montréal, and at age seven, they relocated to Aurora, Ontario. Johnston grew up playing both soccer and hockey and began playing soccer at age four with Lakeshore SC. Off the field, he enjoys sports and art. Growing up, his favourite player was Paul Scholes, and he supported Manchester United. His father was a two-time Canada Soccer National Championships winner with Vancouver Westside FC in 1993 and 1996.

Internationally, Johnston has represented Canada at the FIFA World Cup Qatar 2022. He was part of Canada’s squad that won the Concacaf Final Round of FIFA World Cup Qualifiers (2021–22), earned a Concacaf Silver Medal in the 2022–23 Nations League, reached the semifinals of the 2021 Concacaf Gold Cup, and helped Canada finish fourth at the CONMEBOL Copa América USA 2024.

Johnston is recognized for his defensive reliability, attacking support from the right flank, and versatility, making him a key player for both club and country.