The Swede grew up idolising the legendary Brazilian, who won the FIFA World Player of the Year award twice by the age of 21 and had over 200 goals to his name by the time he turned 23.
Twice the world's most expensive footballer, 'R9' was unplayable on his day and it was only persistent injuries that prevented from achieving even more greatness later on in his career.
Speaking to Discovery Plus, via Goal, Ibrahimovic said: "I don't need to describe Ronaldo, 'The Phenomenon'.
"I always say you have the players that play the game, and the players that are the game. For me, Ronaldo is the game. When you watch him play, everyone wanted to play like him and become like him.
"The way he was moving, the way he did his stepovers, the way he did 'the snake'. The way he was moving, for me he's the greatest player through history, no doubt."
'O Fenomeno' finished his club career with 352 goals in 518 appearances, while he hit 62 in 98 for Brazil - including 15 in World Cup tournaments.
In a solitary season at Barcelona, Ronaldo scored 47 goals in 49 appearances. A young Jose Mourinho saw him up close and personal during that stint and he too shares Ibrahimovic's opinion that 'the original Ronaldo' is the best to ever do it.
Asked by LiveScore who the best player ever is, he replied: "Ronaldo, El Fenomeno. Cristiano Ronaldo and Leo Messi have had longer careers, they have remained at the top every day for 15 years.
"However, if we are talking strictly about talent and skill, nobody surpasses Ronaldo [Nazario]. When he was at Barcelona with Bobby Robson, I realised that he was the best player I'd ever seen take to the field.
"Injuries killed a career that could have been even more incredible, but the talent that that 19-year-old boy had was something incredible."
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