Who was the first unseeded player to win the Australian Open men's singles?

Mark Edmondson was the first unseeded player to win the Australian Open men's singles title. He achieved the feat at the 1976 tournament by defeating defending champion John Newcombe in the final.

Edmondson entered the event ranked world No. 212 and was not among the seeded players. His victory was one of the greatest upsets in Australian Open history, especially because Newcombe was a former world No. 1 and a major champion. Edmondson won the final 6–7, 6–3, 7–6, 6–1.

The tournament was played at Kooyong Lawn Tennis Club in Melbourne on outdoor grass courts, and its dates crossed the end of 1975 and the beginning of 1976. Edmondson's title was the only Grand Slam singles championship of his career.

Another remarkable detail is that he remains the lowest-ranked man to win a singles major since the ATP rankings began in 1973. The question is specifically about an unseeded Australian Open men's champion, so later unseeded winners do not change Edmondson's place in history.