Newcastle United were reportedly in the running to sign the Portugal international before he agreed a loan deal at struggling Ligue 1 side Monaco.
Monaco have signed Portuguese international winger Gelson Martins on loan from Atlético Madrid until the end of the season after the player reportedly rejected a move to Newcastle United.
The 23-year-old has made just eight LaLiga appearances for Diego Simeone's side since his arrival at the Wanda Metropolitano on a free transfer from Sporting CP in July.
He arrives at Monaco with the club second-bottom of Ligue 1 but hopeful of a revival after Leonardo Jardim was reinstated as head coach following Thierry Henry's sacking.
Monaco vice president Vadim Vasilyev told the club's official website: "Welcome to Gelson Martins.
"Gelson is a fast attacking midfielder who has shown great things in the Sporting jersey and who will be able to bring to the squad all his speed and passing abilities."
L’AS Monaco est heureux d’annoncer l’arrivée de Gelson Martins en provenance de l’Atlético Madrid. Le milieu offensif est prêté jusqu’à la fin de la saison.— AS Monaco (@AS_Monaco) January 27, 2019
Gelson's only league start for Atletico came in November, when he partnered Antoine Griezmann in attack as the Frenchman scored in a 1-1 draw with Leganés.
"I am very happy to arrive at AS Monaco," Gelson said. "I cannot wait to get back to the field with my new team-mates and do my best to help the team."