ORLANDO, FL - MARCH 20: Jason Day of Australia hits his tee shot on the ninth hole during the final round of the Arnold Palmer Invitational Presented by MasterCard at Bay Hill Club and Lodge on March 20, 2016 in Orlando, Florida. (Photo by Sam Greenwood/Getty Images)

Australian Jason Day has won the Arnold Palmer Invitational by one stroke to rise to No.2 in the world rankings.

Day, who trailed American Kevin Chappell by one shot heading into the final round, shot a two-under par 70 to finish 17-under to claim a confidence boosting win in the lead up to the US Maters.

The win completes a brilliant month on the PGA Tour for Australians, with Adam Scott winning back to back tournaments in early March.

The win is Day's first tournament victory since the BMW Championship in September last year.

"I just ground out today. It wasn’t the best day that I had, but just to be able to get it done when I wasn’t quite on," Day said.

Fellow Australian Adam Scoot finished in a five-way tie for 12th at nine-under, while Marc Leishman finished one shot further back at eight-under.

The US Masters begins on April 7.