New Zealand paceman Trent Boult has been ruled out of the third Test against Australia after fracturing a finger on Saturday.

Boult, who missed the series opener due to a side strain, was hit on the hand by Mitchell Starc during day three of the second Test in Melbourne.

The left-armer bowled during Australia's second innings before the Black Caps announced he had fractured a finger on his right hand.

"Trent Boult will return home to New Zealand following the second Test after suffering a fracture to the second-metacarpal of his right hand while batting on day three," they wrote on Twitter at the close of play.

"He will require around four weeks of rehabilitation. A replacement player will be confirmed in due course."

New Zealand are staring at a 2-0 deficit in the three-Test series, which will conclude in Sydney beginning on January 3.

Australia are 137-4 in their second innings, leading by 456 runs at the MCG.