After two weeks of negotiations between the two clubs, the 30-year-old striker finally signed an 18-month contract with the Italian giants for a fee believed to be 7.5 million euros (9.7 million dollars).

The transfer brings Ronaldo back to northern Italy after a near five-year absence having played for Milan's city rivals Inter for five years before signing for Real in 2002.

"I hope I can fulfil the dreams of the AC Milan fans," Ronaldo said on his arrival at Milan's Linate airport.

"It's all a bit overwhelming, but I am happy to be here and glad that the transfer has finally gone through. It's a great feeling to be back in Milan."

Earlier Ronaldo had expressed his sadness at leaving Real before jumping on the plane from Madrid.

"It's sad to say goodbye after four-and-a-half years, but now I have an important challenge ahead of me," said the Brazil international.

"It hurts me to leave, it breaks my heart, but that's life."

Ronaldo, the highest scorer in World Cup history with 15 goals, had fallen out of favour with Real coach Fabio Capello and was becoming increasingly frustrated at his lack of first-team football.

And he couldn't resist taking a final swipe at Capello before saying 'adios' to the Spanish capital.

"I want to thank the fans and all the coaches that I've worked with -- except one," said the three-time FIFA World Player of the Year.

Ronaldo then softened up, saying his relationship with Capello was not as bad as reported in the press.

"Lots of things have been said, but I've never had the slightest problem with the coach," he said.

"He didn't want me, and I am a professional. I want to play and I needed to find a solution."

Ronaldo will not be able to play for Milan in the Champions League this season having already played in the competition for Real.

Milan, whose title hopes have been dashed by an eight-point penalty for match-fixing, are only three points adrift of fourth place and will be looking to the Brazilian's goalscoring prowess to help them clinch one of the four Champions League places up for grabs.

Born in Bento Ribeiro, in Rio de Janeiro, Brazil, Ronaldo first came to prominence with Cruzeiro where he scored 58 goals in 60 appearances.

After making his international debut for Brazil at the age of 17, he left to join PSV Eindhoven in 1994.

In his two seasons in Holland, he scored 55 goals in 56 appearances and his astonishing strike rate didn't go unnoticed across the continent, with Spanish giants Barcelona snapping him up two years later.

Ronaldo continued to find the net with alarming regularity, scoring 39 goals in 44 appearances in his one and only season at the Nou Camp before Inter lured him to Italy for 25 million euros (32.3 million dollars).

In his first season he scored 34 goals in 47 matches before helping Brazil reach the 1998 World Cup final against hosts France.

The stage was all set for Ronaldo to shine only for a mystery illness to lay him low on the day of the match.

After first being named as a substitute, he was then included in the starting line-up but looked a shadow of his true self as Brazil lost 3-0.

In November 1989 he ruptured his knee-cap tendon while playing for Inter and was ruled out for four months.

He made his comeback as a substitute in the Italian Cup final, but just six minutes after coming on his knee gave way and he was carried off in floods of tears.

After two operations and months of rehabilitation, Ronaldo returned to lead Brazil's attack at the 2002 World Cup in Japan and South Korea and helped them to their fifth title, netting both goals in a 2-0 win over Germany in the Yokohama final.

Shortly after the final, he announced he wanted to leave Inter after Real came in for him.

Inter were furious having stood by the Brazilian during his injury crisis, but Ronaldo turned his back and left for Spain in a deal worth an estimated 45 million euros (58 million dollars).

He scored within a minute of his Real debut and went on to bag 99 goals in 164 appearances for the Spanish giants before his relationship with Capello came to a head.

Ronaldo's departure follows that of Luis Figo, the retirement of Zinedine Zidane and the soon to be departed former England captain David Beckham, bringing an end to the so-called Galacticos era.