The England international smashed his effort towards the top left corner of the goal, leaving Thibaut Courtois absolutely no chance to give the Catalans a ninth-minute lead.
With that, Rashford becomes the first Barcelona player to score directly from a set-piece in the fixture since Lionel Messi in October 2012.
Ferran Torres doubled Blaugrana’s lead in the 18th minute as the Camp Nou giants moved closer to winning a 29th Spanish top-flight title.
Rashford’s effort was his eighth goal of the 2025/26 campaign, with his last strike coming in Barcelona’s 2-0 win at Getafe.