William Joseph "Billy" MacLellan (born 31 January 1974; age 51) is a Canadian actor who portrayed Barlow in the Star Trek: Discovery first season episode "Vaulting Ambition".
MacLellan has had a long career mostly in television, where he appeared in guest roles on series such as Sue Thomas: F.B.Eye, ReGenesis (starring Conrad Pla), Rookie Blue (with Melanie Nicholls-King), Heartland, Republic of Doyle (with Victor Garber), Combat Hospital (with Lisa Berry), Saving Hope (starring Huse Madhavji, with Gia Sandhu), Covert Affairs (with Oded Fehr), Nikita, The Expanse (starring Shawn Doyle and Shohreh Aghdashloo, with Tig Fong), Terry Matalas' 12 Monkeys (with Alisen Down and Andreas Apergis), Dark Matter (with Roger Cross), Wynonna Earp (starring Melanie Scrofano), Killjoys (with Atticus Mitchell), and Murdoch Mysteries (with Sara Mitich).
In 2015, MacLellan had a recurring role in Defiance. He co-starred in Bellevue alongside Shawn Doyle, Cameron Roberts, and Andreas Apergis. In 2022, he played recurring roles in the shows In the Dark and Pretty Hard Cases (starring Karen Robinson).
He also appeared in the television movies Ultra (2006, with Richard Leacock), An Amish Murder (2013), Catch a Christmas Star (2013), Netflix' The Silence (2019), and Christmas on the Rocks (2022). His film credits include October Gale (2014), Maudie (2016), Ice Blue (2017), Goalie (2019), Nobody (2021, starring Christopher Lloyd), and Delia's Gone (2022).