Lazio took advantage of an off-kilter Bayern Munich to edge out a possibly decisive win in the first leg of their Champions League Round of 16 tie.
The Biancocelesti booked their spot in the knockout stages of the competition after securing a second-place finish in their group, just behind Atletico Madrid and ahead of Feyenoord and Celtic.
Bayern Munich were almost flawless in their Champions League group stage, winning all but one of their games to top a group containing Manchester United, FC Copenhagen and Galatasaray.
Heading into the match, Lazio found a key boost in confidence after beating Cagliari away, whilst Bayern were knocked off base after losing a vital head-to-head clash with Bundesliga leaders Bayer Leverkusen, who have now taken a five-point lead at the top of the table.
Bayern got off to a strong start at the Stadio Olimpico and had their first real chance in the seventh minute, when a lofted pass from Thomas Muller allowed Harry Kane a shot from just seven yards out in the seventh minute. His attempt sailed over the crossbar, letting Lazio off the hook.
The Biancocelesti tried to respond and had a decent chance with Luis Alberto, before a Leroy Sane freekick later in the first half caused a brief scare for the home fans.
Bayern tried to push for an advantage in the closing stages of the first half but resilient defensive work by Lazio limited their chances, keeping their xG at 0.39 for the first 45 minutes, a respectable number considering the balance of play.
Lazio came out in the second half swinging and had a glorious chance to go 1-0 up in the 48th minute when a great ball from Luis Alberto put Gustav Isaksen in a 1-on-1 scenario. The talented winger overthought his shot and ultimately allowed Manuel Neuer to make a save.
In the 66th minute, everything changed. Isaksen was fouled by Dayot Upamecano in the penalty area, receiving a stomp on his ankle, and the Bayern defender was shown a red card. The referee pointed to the stop, giving Immobile his most important penalty in recent memory.
The Lazio captain did not disappoint from the spot, calmy dispatching the strike to put the home side 1-0 up, sending the fans in the Stadio Olimpico wild.
Bayern tried to push for an equaliser after this but Lazio remained stubborn, holding their resolve to see out a key 1-0 win over the German giants, giving them a real chance of securing the upset in the second leg.
Too bad that Felipe Anderson ruined that big chance of making it 2-0, it will be tough and rough in the second leg.