Atletico went into the game needing a victory and hoping AC Milan failed to beat Liverpool in the other group B match.
And Diego Simeone's side got what they desired as they prevailed 3-1 in Portugal.
But the scoreline doesn't tell the full story. Not in the slightest.
The second half was absolute chaos as referee Clément Turpin brandished three red cards and three yellow cards in just a matter of minutes.
Yannick Carrasco was the first player to receive his marching orders as he was sent off after lashing out at Otavio.
Carnage then followed over the next few minutes.
Atletico's Angel Correa, as well as Porto duo Otavio and Pepe, were both shown yellow cards as tensions boiled over.
Pepe was given his booking after screaming in the face of Mario Hermoso.
Three minutes later and Porto were reduced to 10-men.
Matheus Cunha charged towards Wendell to retrieve the ball after it had gone out of play.
The Brazilian full-back raised his arm and appeared to catch Cunha with his elbow.
It did not look intentional - and there wasn't much contact - but that didn't stop Cunha throwing himself to the floor.
It then all kicked off again.
Porto's backup goalkeeper Agustín Marchesín was also sent off in the resulting melee.
VAR saved Arsenal from taking a BEATING at Everton! Full reaction on The Football Terrace...
There were then three goals in stoppage time to put gloss on what was just a crazy, crazy game.
Atletico will be in the hat for the Champions League last-16 draw, which takes place in Nyon, Switzerland on Monday.
Porto meanwhile have dropped down into the Europa League.