"Cristiano Ronaldo was greeted by a huge crowd of adoring fans as he was officially unveiled as a Real Madrid player on Monday evening.
The former Manchester United player, who moved to the Bernabeu in a world record £80m deal, said that it was a "childhood dream" to sign for the Spanish giants.
It is thought 80,000 fans flocked to the club's stadium for the event - the largest such gathering since Diego Maradona attracted 75,000 when signing for Napoli from Barcelona in 1984.
"I am just so happy to be here,'' he told the supporters inside the ground. "For me, I have made my childhood dream a reality, which was nothing less than playing for Real Madrid.
"I didn't expect a jam-packed stadium - this is truly impressive.''
Speaking at a press conference after his presentation, Ronaldo again said that Real are "the closest club to my heart'' - but admitted it was a wrench to leave England.
"Thank you to all (United) supporters, the boss (Sir Alex Ferguson), friends and team-mates - I've been there six years and have friends there. But people respect my decision,'' he said.
"The great challenge now, and dream, is to play at Real Madrid but I'm going to miss many things in Manchester.''
He said there was no bad blood over his exit. "It was good,'' he said of his departure. "My relationship with him [Sir Alex Ferguson] was always good and will stay that way forever.
"I went to Manchester, spoke to them and everything was fine. Life goes on.''
On his transfer fee, he added: "I have always thought that the best clubs, to have the best players, have to pay - so Real Madrid did a good thing. It was a correct decision.
"I understand...it is not your everyday thing to manage these figures, but I'm happy to be the most expensive player in the history of football and I'm going to prove that they paid good money for me and it was worth it.''
Ronaldo will wear the number nine shirt. Ronaldo registered the CR9 trademark at the start of the year.
Returning Real president Florentino Perez said: "We are very satisfied to know that you made the firm decision to play for Real Madrid. They [the fans] will ask of you the very best, but will also give you their all.''
As with Kaka last week, Ronaldo was brought out onto a stage which displayed all of the club's European Cups.
Raul Albiol has also signed with Karim Benzema set to move from Lyon shortly.
Ronaldo completed his medical earlier on Monday with Carlos Diez, Real's medical chief, told the club's official website: "(Ronaldo) is in perfect condition and very eager to start the season as soon as possible.
"He has an extraordinary cardiac and lung capacity. We have complemented everything that we already did in Portugal and done all the specific tests.
"Now we will be able to start working using an individual plan in order to improve his performance.
"For him (Ronaldo), it's a dream, and this dream starts to convert into reality from today.''"