Australian open was started in 1905 and was a grass court tournament until the year 1987, after which the surface was changed to hard court. Who is the only player to have won the Australian open on both grass and hard court?

Mats Wilander won the Australian Open in 1983 on grass courts and again in 1984 after the surface changed to hard courts (Rebound Ace). He remains the only player to have won the Australian Open on both grass and hard court surfaces. This unique feat occurred during the transition period when the tournament switched surfaces.