Luka Modric beat a record previously held by Ferenc Puskas as he starred in Real Madrid's 2-2 draw at Bayern Munich.
The Croatian came off the bench on Tuesday night in the 75th minute, replacing Jude Bellingham, who had had a muted night by his standards.
That made him the oldest player ever to feature for Real Madrid in the Champions League.
Puskas held the record since his final season of 1965/66, when he turned out aged 38 years and 229 days old.
Modric has now pinched the bragging rights by five days, turning out aged 38 years and 234 days.
Luka Modric became Real Madrid's oldest-ever Champions League player when he replaced Jude Bellingham on Tuesday
Aged 38 years and 234 days, he contributed to the 2-2 draw with Bayern Munich
Club legend Ferenc Puskas had previously held the record from the 1965/66 campaign
With Madrid bringing a draw back to the Bernabeu, there is every chance that he will get to extend his record not just in the semi-final second leg but also in the final.
Modric's longevity is remarkable and he is still a key player for Los Blancos, making 40 outings this term.
While many other members of Madrid's old guard have moved to new pastures and retirement homes, Modric's ambition is to keep playing at the highest level.
Alongside this record, he has also made the most appearances over the age of 35.
He has some way to go to reach Iker Casillas' crown jewel of 162 games in the Champions League for the club, but with 118, Modric has done a stellar job.
If they offer Modric a new deal - his current contract expires in the summer - he could overtake Puskas to become their oldest-ever player.
The indications earlier in the season were that Modric would depart, but more recently it has emerged that he would like to stay.
He is likely to add a LaLiga title to his tally of trophies and could well lift a sixth Champions League trophy, which would set a new record alongside fellow Madrid stalwart Dani Carvajal.