Rangers kicked off their Europa League Group D campaign with a 2-0 win away to Standard Liege. James Tavernier opened the scoring with a first-half penalty and Kemar Roofe netted a spectacular second from the halfway line in stoppage time.
In the other Group D tie, Benfica were 4-2 winners away to Lech Poznan, who Rangers face at Ibrox in matchday two next Thursday.
Celtic went down 3-1 at home to AC Milan in Europa League Group H. The Serie A leaders were two goals in front at half-time but Mohamed Elyounoussi pulled one back for Neil Lennon's men with 14 minutes left. Milan then scored their third goal in added time.
In the other Group H fixture this evening, Lille - who host Celtic next week - ran out 4-1 winners away to Sparta Prague.