Daryl Ernest O'Brien (born 10 September 1941) is a former Australian rules footballer who played 135 games for the North Melbourne in the Victorian Football League (VFL) during the 1960s. A tenacious utility player who often started on the half-back flank, he was also considered one of the toughest and most effective "taggers" of the period and one of the hardest men to beat one-on-one in the league. O'Brien's tagging role embodied a who's who of top players of that era, including Ron Barassi, Bobby Skilton, Peter Hudson, Alex Jesaulenko, Peter Crimmins, Darrel Baldock, Roger Dean, John Sharrock, Des Tuddenham, Ted Whitten and John Northey.