Note: Single-source report; awaiting corroboration.
Cristiano Ronaldo leads all players in UEFA Champions League semi-final appearances, playing 21 times for Manchester United and Real Madrid. He is followed by Toni Kroos with 20 appearances, and Karim Benzema and Luka Modrić with 18 each.
For goals scored in the semi-finals, Ronaldo also holds the record with 13 goals, ahead of Karim Benzema with eight and Robert Lewandowski with seven.
Lewandowski holds the individual record for most goals scored in a single Champions League semi-final game and tie, netting four times for Borussia Dortmund against Real Madrid in the 2012/13 season.
Regarding age records, Mark Schwarzer is the oldest player to feature in a Champions League semi-final, appearing for Chelsea against Atlético Madrid on 30 April 2014 at 41 years and 206 days.