Velez Sarsfield wrapped up the Apertura title with a game to spare courtesy of a 2-0 victory over botton club Union Santa Fe.
The title, which is the club's ninth overall, was wrapped up when Facundo Ferreyra scored in the 49th and 85th minutes to earn all three points for the Buenos Aires-based side.
Lanus could have made the title race go to the final round had they beaten River Plate but instead they slipped to a 1-0 defeat, Rodrigo Mora the scorer.
That left Velez five points clear of both Lanus and Belgrano. The latter won 1-0 at home to Tigre, with Cesar Pereyra on target.
Boca Juniors are heading to the Copa Libertadores despite a 1-0 at Arsenal Sarandi, who had Emilio Zelaya to thank for the win.
Elsewhere, San Lorenzo defeated visiting Independiente 2-1.
Osmar Ferreyra scored first for the visitors after nine minutes but Nicolas Arce and Alan Ruiz hit back for San Lorenzo. Both sides finished with 10 man as Gonzalo Prosperi and Julian Velazquez saw red in the closing stages.