33-year-old Antunes was a free agent after leaving Getafe when his contract expired in June.
And following seven and a half seasons between Spain and the Ukraine, the left-back has returned to Portugal.
Antunes has signed a two-year contract with Sporting and brings a wealth of experience to Rubin Amorim’s side.
Antunes, capped 13 times by Portugal, left his homeland for Roma in 2007 and has been playing in Spain recently.
His performances in the 2018-19 season led to him being named in the La Liga Team of the Season.
“It is sensational to come back to Portugal and to do it to represent a club like Sporting,” he said. “Playing in Portuguese football was my childhood dream and I realize it now.”
Porro on loan
Sporting’s other signing today is right-back Pedro Porro, who is owned by Manchester City.
Porro, 20, has moved to Sporting on an initial two-year loan with an option to buy.
He made 15 appearances in total for Valladolid and will hope to play more regularly in Lisbon.