Valencia presented new signing Nani on Thursday in front of more than 12,000 fans at the Mestalla.
Last week, Nani completed a move to the La Liga club on a three-year contract after just 12 months at Fenerbahce.
"This is a very special day for me," Nani told the crowd. "I'm happy to joining a great club and I hope to be at Valencia CF for many years to come.
"I thank [sporting director] Suso and [club director] Kim Koh for their interest in signing me, and now I hope to repay that confidence they have placed in me with hard work, dedication and goals."
The transfer fee between the two clubs was agreed during the European Championship and the winger has now signed his new contract after Portugal's Euro 2016 triumph.
- Valencia CF English (@valenciacf_en) July 14, 2016
Nani, who has 103 caps for his country, played in every game of the tournament. including the 1-0 extra-time victory over the hosts in the final.
"I know some players and I've had the chance to talk to the coach today," Nani said on Thursday after meeting his new teammates and manager Pako Ayestaran.
"I chose Valencia because it was the best option for me.''
The 29-year-old started his career at Sporting Lisbon, where he played 64 times before a big-money move to Manchester United in 2007.
He made 229 appearances for the Red Devils during an eight-year spell at Old Trafford, scoring 40 goals during a successful period in which he won 12 trophies including four Premier League titles before moving to Turkey last summer.