Mitchell Johnson pushed a single off the first ball of the final over, giving Hussey the strike with just five balls remaining. Facing spin bowl Saeed Ajmal, the left-hander threw caution to the wind, with spectacular results.
He immediately pulled a short ball over mid-wicket for six, signalling his intent for the final four balls. He then smashed the next delivery out of the ground. With two balls left Australia needed five runs to win, and Hussey hit a four with a slashing stroke backward of point.
Pakistan set the field close in an effort to prevent Australia scoring the single they needed to win, but Hussey was in no mood to capitulate, launching the final delivery over long-on for six and booking Australia's place in the final.
"By the end I was just swinging through the ball there ... it was probably one of the best innings of my life," said Hussey after completing the biggest successful run chase in this year's tournament.
Australia skipper Michael Clarke said that batsman was an "absolute freak".
"Once Cameron got out I thought it was going to be really tough but with Hussey in, you never know."
The result sets up a hotly anticipated "Ashes final" against Test rivals England, who booked their place with a slick victory over Sri Lanka on Thursday. "England are playing some great cricket so it's going to be a fantastic final," Clarke said.
Victory on Sunday would give Australia, holders the 50-over World Cup and the Champions Trophy, all three international cricket titles.