Quito: Lionel Messi scored a hat trick when he was needed most, rallying his country to a 3-1 win over Ecuador and a spot in Russia next summer.
Argentina started the final night of South American qualifying in sixth place, with only the top four qualifying for the World Cup while the fifth goes to an intercontinental playoff against New Zealand.
Argentina likely needed a win to avoid elimination, but they were behind immediately, as Ecuador scored in the opening minute.
The five-time world player of the year equalised after 12 minutes when he linked up with ex-Manchester United midfielder Angel di Maria and stabbed home.
His second goal came eight minutes later with a powerful strike from the edge of the area before a fine solo goal in the second half sealed the victory.