Morris will replace countryman Chris Tremain at Wantage Road, and will be available for three matches from the fourth round of Championship fixtures
Northamptonshire have added a second Australian bowler to their County Championship arsenal.
Lance Morris will join Northants later this summer, after taking 31 wickets in six matches in the Sheffield Shield. He averaged just 19 with the ball and was the winner of the Bradman Young Cricketer of the Year, earning a callup to the Australia Test team.
He will replace countryman Chris Tremain at Wantage Road, and will be available for three matches from the fourth round of Championship fixtures.
Morris will meet up with his Western Australia teammate and captain Sam Whiteman during the stint at Northants.

Western Australia seamer Lance Morris [Getty Images]
"It'll be great to link up with Sam [Whiteman] and hopefully help deliver some positive results for the team while I'm there," he said.
Morris, who is capable of clocking speeds of 90mph, will be embarking on his first spell in the UK.
Northamptonshire bowling coach Chris Liddle is excited to have him in the squad.
"He possesses express pace and has been highly talked about, I'm looking forward to seeing him charging in wearing a Northamptonshire shirt," Liddle said.
Morris can't wait to get started, saying: "You hear people talk a lot about county cricket so I'm excited for a new experience."