It pits last season's semi-finalists from the premier European competition and the Europa League.
Good start for both teams in 2025/26
For the Gunners it was their third UCL semi-final in their history, whilst Athletic's return to the competition for the first time in 11 years is only the third time they've competed in it (also 1998/99 and 2014/15) since the rebranding to the Champions League.
Both teams have started this season in good form, with Mikel Arteta's side having won three of their four Premier League games in 2025/26. They sit second in the table as a result and have conceded just the one goal - to leaders Liverpool - so far this season.
Ernesto Valverde's Lions are perched in fourth position in the LaLiga table and have an identical record in terms of three wins and one loss, which came the past weekend against Alaves. Just six goals scored and four conceded is an indicator of how tight the Basque outfit like to keep things.
They were no match for Arsenal in a pre-season friendly which took place at the Emirates Stadium, however. On that occasion, the hosts ran out comfortable 3-0 winners with goals from Viktor Gyokeres, Bukayo Saka and Kai Havertz.
Reading too much into that result would be a little foolish, given that this is the first official meeting between the two teams.
First-half goals expected
Valverde has been an opposition manager against the north Londoners twice before, when in charge of Olympiacos during the group stages of the Champions League in the 2011/12 season. In both matches, he went with a 4-3-2-1 formation, winning 3-1 in Greece but losing the return 2-1 at the Emirates.
In their last six matches in all competitions, Athletic have won three and lost three, scoring six and conceding 10. Three of those games have seen them score first, twice in the first half.
Arsenal have won five and lost one of their previous half-dozen games, scoring 14 goals and conceding twice.
Half of those goals have been scored in the first 45 minutes, and the north Londoners have been on the scoresheet first in five of the six matches.
In each of the six games the Gunners haven't conceded before the break, suggesting that Los Leones will have their work cut out, particularly as talisman Nico Williams will be missing through injury.
Unai Egiluz is also on the treatment table whilst Alex Padilla is suspended, Yeray Alvarez is serving a ban for a doping offence, and Aymeric Laporte is ineligible.
Arsenal's injury problems mount
Arsenal have problems of their own with Martin Odegaard picking up an injury in the weekend game against Nottingham Forest and thus joining Havertz, Saka and Gabriel Jesus on the sidelines. William Saliba and Christian Norgaard will face late fitness tests to determine if they'll be risked or not.
Though records at this stage mean little, the Gunners could still complete an unprecedented European feat should they win the game.
If they head back to north London victorious, they will have become the first side ever to beat Spanish teams six games in a row in the European Cup/Champions League, having already despatched Real Madrid (twice), Sevilla (twice) and Girona since 2023.
They have only won 17 of their 39 European fixtures against Spanish opposition, however.
Athletic have won six and drawn four of their 20 matches against English opponents in European competition, and not since 2012, when they beat Sir Alex Ferguson’s Man Utd have they emerged with a win.
Athletic's motivation
The Basques' ability to grind out results and play on the counter-attack when necessary could frustrate visitors who will want to take the game by the scruff of the neck and enjoy the vast majority of possession.
The hosts have the memories of that 7-1 aggregate semi-final loss to Man Utd in last season's Europa League still fresh in their minds of course, and that's more than enough motivation to ensure they are not walked all over again by an English top-flight team.
Whilst it won't be factor in the result, a fascinating sub-plot is the emerging Arsenal link with Athletic's major rivals, Real Sociedad.
Arteta played for La Real before a transfer to Everton and then on to the Gunners, whilst all of Odegaard, Mikel Merino and Martin Zubimendi were signed by Arsenal from Real Sociedad.
Whatever the result on Tuesday there is plenty of Champions League football to play thereafter, but getting off to a good start with points on the board is of obvious benefit.
