Substitute Sergio Floccari sealed Lazio's place in the Coppa Italia final as his last-gasp effort helped them to a 3-2 aggregate win over Juventus.
Floccari rose highest to head home from a corner in the fifth minute of injury time to give his side a 2-1 win on the night.
His goal came mere moments after Arturo Vidal looked to have sent the tie into extra-time after stepping inside his marker to rifle into the net from close range.
Lazio midfielder Alvaro Gonzalez broke the deadlock in the 53rd minute with a fine diving header and it looked like that would be enough to separate the teams, who drew 1-1 at in Turin last week, before the late drama occurred.
The Biancocelesti will meet either fierce rivals Roma or Inter Milan at the Stadio Olimpico in the final. Roma must wait until April 17 to try and consolidate their 2-1 first-leg lead.