It was third time lucky for the Sydney 57-year-old after being nominated for The Dark Knight in 2009 and Master and Commander: The Far Side of the World in 2004 but left both ceremonies empty-handed.

"This is the most awesome thing that can happen to a guy like me," Smith told the the A-List crowd at the 90th Academy Awards at Hollywood's Dolby Theatre on Sunday.

Smith, who started his movie career as a 16-year-old making coffee at a Sydney film production business, has formed a strong bond with Dunkirk's British director Christopher Nolan.

Dunkirk was the seventh film they have collaborated on.

Smith joked that Nolan was also an editor, but he was "happy" that Nolan did not handle the editing equipment when they worked.

Smith's win is the fourth time in seven years an Australian has won the editing category.

Another Aussie, Paul Machliss, was nominated in the category on Sunday for his editing work on the action film Baby Driver.

Australian duo Josh Lawson and Derin Seale have missed out on the live action short Oscar for their comedy The Eleven O'Clock.

Lawson, who starred in and wrote the 13-minute, Sydney-shot film, and Seale, who directed it, were considered outsiders for the Oscar.

The Oscar went to The Silent Child at the 90th Academy Awards underway at the Dolby Theatre in Hollywood on Sunday.

Margot Robbie is the only other Australian still in contention for the coveted best actress Oscar for her role striking performance as controversy-plagued US Olympic ice skater Tonya Harding in I, Tonya.

Robbie and acting great Meryl Streep (The Post), are given little chance of winning, with Frances McDormand (Three Billboards Outside Ebbing, Missouri) the front runner followed by Saoirse Ronan (Lady Bird) and Sally Hawkins (The Shape of Water).

Australian Associated Press