The 39-year-old struck for Portugal in their Nations League game against Croatia, putting them 2-0 up.
It prompted an emotional celebration by the forward, as he dropped to his knees by the corner flag in tears.
The goal was his 131st for his country, while he has also scored at club level for Sporting Lisbon, Manchester United, Real Madrid, Juventus and current club Al-Nassr.
“It was emotional because it’s a milestone,” Ronaldo said. “It seems like any other milestone but only I know, and the people around me, how hard it is to work every day, to be physically and psychologically fit, to score 900 goals.
“It’s a unique milestone in my career.”
Such is Ronaldo’s longevity that if someone was born when he scored the first competitive goal of his career they would now be 21.
He struck a double for Portugal’s Sporting on 7 October 2002 at the age of 17 years, eight months and three days in a 3-0 win against Moreirense.
He then moved to Manchester United, scoring 118 goals in 293 games for the Red Devils before joining Real Madrid in 2009 for a then world record 94m euros (£80m).
In nine years at the Spanish giants, he scored 450 goals in just 438 games before making the move to Italy to join Juventus.
He added another 101 goals to his tally during his three years with the Italian club before returning to United, where he would score 27 goals in 54 games.
But a return to the Red Devils did not have a fairytale ending - and in 2023 he made the move to Saudi Arabia with Al-Nassr, where he has got 68 goals and counting.
Incredibly, almost half of Ronaldo’s goals (437) have been scored since he turned 30 in February 2015.