MLB star Manny Machado has made US sports history in signing the most lucrative free agent contract ever.

Machado inked a ten-year contract with the San Diego Padres worth $USD300 million ($AUD420 million).

The 26-year-old is a four-time All-Star and has overtaken Alex Rodriguez's $USD275 million for the free agent contract record.

He sits behind only Giancarlo Stanton's 2014 $USD325 million extension with the Miami Marlins for the biggest contract ever signed in US professional sport.