Hussey hit six sixes in all to finish with an unbeaten 60 in just 24 deliveries as Australia passed Pakistan's 191 for six, the joint second highest score of this tournament, with a ball to spare to clinch a final meeting with England on Sunday.
Australia were in trouble at 62 for four in the ninth over but then Cameron White blasted five sixes in his 43 off 31 balls to get his side back in the game.
When White went in the 17th over it still looked a long shot for Michael Clarke's men with 53 needed from 3.3 overs.
That was reduced to 34 off two overs and then 18 from the final over by spinner Saeed Ajmal.
Mitchell Johnson pushed a single to give Hussey the strike and the left-hander responded with some astonishing batting.
He pulled a quicker short ball over the mid-wicket boundary and then blasted the next delivery way over long-on.
Hussey followed up by slashing a four backward of point before whacking the penultimate delivery for another six over long-on.
"By the end I was just swinging through the ball there ...
it was probably one of the best innings of my life," said Hussey.
Earlier, brothers Kamran and Umar Akmal struck half-centuries as Pakistan piled up an imposing total of 191 for six.
