South Korea have become the 14th team to join hosts Qatar and book a place at the 2022 World Cup following a 2-0 defeat of Syria in Dubai.
They join Iran as the two automatic qualifiers from Asian group A - Australia are in group B.
Two matches remain to be played in the group but South Korea cannot now be caught after goals from Kim Jin-su and Kwon Chang-hoon in the 53rd and 71st minutes earned victory.
Qatar will be South Korea's tenth successive appearance at the finals.
Elsewhere in the group Iran beat United Arab Emirates 1-0 and Lebanon drew 1-1 with Iraq.
Iran won despite the 49th-minute dismissal of Sadegh Moharrami. Five minutes earlier Mehdi Taremi had scored what proved the winning goal.
The results left UAE in third, three points clear of Lebanon.
The third-placed team qualifies for a play-off with the equivalent team in group B, currently Australia, with the winner facing a play-off with a South American team to reach Qatar.