Lleyton Hewitt will come out of retirement again to play doubles at the ATP Estoril clay-court tournament in Portugal with emerging Australian talent Alex de Minaur.

"We have a wild card, we have the ex-world-number-one Lleyton Hewitt ... Who will break from 'retirement' to play at the Millennium Estoril Open alongside countryman Alex de Minaur," tournament organisers tweeted.

Lleyton Hewitt will play doubles with Alex de Minaur in Portugal. Credit:AAP

Davis Cup captain Hewitt retired from professional tennis in 2016 but made a cameo appearance alongside Sam Groth at the Australian Open where the duo made the quarter-finals.

Hewitt, the youngest man to be ranked No.1 in world singles, won the 2001 US Open and 2002 Wimbledon titles just a few years after his doubles partner de Minaur was born.