With seconds left on the clock, Provedel ventured forward for a corner kick and connected perfectly with Luis Alberto's cross, nodding the ball into the net.
The Lazio players erupted in joy, rushing to celebrate with their goalkeeper-turned-scorer.
Atletico Madrid had taken the lead in the first half through a deflected strike from Pablo Barrios.
This remarkable feat makes Provedel the fourth goalkeeper in Champions League history to score, joining a select group that includes Jorg Butt (who scored three penalties between 2000 and 2009), Sinan Bolat (December 2009), and Vincent Enyeama (September 2010).
Provedel's header also makes him just the second goalkeeper ever to score from open play in the Champions League.
Sinan Bolat achieved this previously with a 95th-minute equalizer for Standard Liege against AZ Alkmaar.
Ivan Provedel's unexpected heroics secured Lazio a valuable point in Group E of the Champions League.
