The Belgian midfielder hit a beauty from 25 yards with just 30 seconds of normal time remaining to secure a 1-1 draw at the Stade de Gerland and a 3-2 win on aggregate in the Europa League, Round of 32 tie on Thursday night. We now take on Inter Milan in the Round of 16.
Mousa's strike was reward for a impressive second half display against Lyon, the Ligue 1 title-chasers steeped in European tradition.
As he revealed later, the lads were determined to get the job done after Lyon took the lead in the first half to level up the tie on aggregate.
"It felt very good (to score) and it was an important goal for us, that makes it even more special," said Mousa.
"I thought we started well but then it was difficult for us, Lyon scored a goal, somewhat surprisingly, but after that we came back into it.
"In the second half we came out of the dressing room and said ‘okay, it’s everything or nothing’ and I’m very happy I could score as well.
"We have top players and it was important in the dressing room (at half-time) to wake everyone up.
"The gaffer did it as well. We all said ‘let’s go guys’. The first half wasn’t that good, we needed to be better and create things, to fight for each other and everyone did that. We’re delighted."