Resilient Scotland shut out Ronaldo's Portugal to end miserable run
The home side needed a wonder save from Craig Gordon to deny Bruno Fernandes a winner in the closing stages, but held out to secure their first point in the top tier of the Nations League.
Portugal remain on top of Group A1 but were made to wait to book their place in March's quarter-finals.
On his 216th international appearance, Ronaldo made his 200th start for his country, more than 21 years on from his first.
However, the 39-year-old failed to add to his 133 Portugal goals and stormed off the field at full-time ranting at the officials.
Scotland have won just one of their last 16 games - a 2-0 friendly victory over Gibraltar in June - and remain without a victory in a competitive match for over a year.
But Steve Clarke's men battled hard to stop the rot in Glasgow.
Scotland even had the best chance of the first half inside the opening five minutes when Scott McTominay headed too close to Diogo Costa from point-blank range.
Portugal quickly took control of possession without creating clear-cut chances.
Francisco Conceicao spooned over early in the second period from Ronaldo's lay-off.
Ronaldo then fired inches wide after making himself room for a shot amid a flurry of desperate challenges from Scottish defenders.
But it was Fernandes who had the best chance to claim all three points when the Manchester United captain's powerful low strike was brilliantly parried by Gordon and collected at the second attempt by the 41-year-old goalkeeper.
Scotland are still on course for relegation from the top tier of the Nations League as they trail Poland, who drew 3-3 with Croatia, by three points with two games remaining.
Croatia sit second, three points behind the Portuguese, who they host next month.
