Which Australian has won the fim world motorcycle championship 5 times?

Mick Doohan, won five FIM World Motorcycle championships in the 500cc category; 1994, 1995, 1996, 1997 and 1998.

He has won the third most 500cc/Moto GP World Championships, only trailing Giacomo Agostini (8 500cc titles) and Valentino Rossi (1 500cc titles, 6 Moto GP titles).

*THe FIM World Motorcycle Championship has existed since 1949 but in 2002 it was renamed to Moto GP.