PSG look to join the very exclusive crop of teams that won the trophy thrice in a row. Slovan Bratislava successfully navigated three playoff rounds.
Match Replays
Sporting CP lost some prominent pieces in the transfer market during the summer, while Galatasaray had the opposite kind of window, adding more stars.
Liverpool ran rampant in last year's group stage before eventually being topped by PSG. Atlético Madrid capitulated to Arsenal in the semi-finals.
Napoli will have their work cut out for them in their UEFA Champions League return, hosting last year's runner-ups, Arsenal, in the opening contest.
Stuttgart qualified for the top continental cup thanks to a fourth-place finish in the Bundesliga, while Viking bested Dinamo Zagreb in the playoff.
Barcelona's run came to an end in the semi-finals against Atletico Madrid last year. Feyenoord are back in the competition following a short hiatus.
Real Madrid and Inter had fairly disappointing continental campaigns, as the former exited in the quarter-finals, while the Italian side even earlier.
Porto didn't get past the Round of 16 in their last two participations. Man. City will try to go all the way under Maresca after a fairly early exit.
Real Betis are making their first UEFA Champions League appearance in 21 years. Lille are playing with the current format for the first time.
Both sides seek improvements, as Villarreal logged just one point in the group stage last year, while Borussia Dortmund bowed out shortly thereafter.
Club Brugge finished 19th in the group phase before being knocked out by Atletico Madrid. Aston Villa qualified by winning the UEFA Europa League.
AEK Athens eliminated Levski Sofia in the playoff to advance to the main stage. LASK pulled off the upset versus Celtic, coming back from a 3-0 loss.