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)

World No.1 Jason Day is reportedly set to sign a lucrative deal with sporting giants Nike, according to ESPN.

Day is set to sign a deal worth $US10 million ($AU 13.4 million) annually to wear Nike apparel.

The Australian has spent the past 25 weeks at No.1, the most weeks in the top spot since Rory Mcllroy from August 2014 and August 2015.