This year Jakob became only the 5th man in history to run sub-3:30 3x in a single season. El Guerrouj is the only man with more than one such season, having done it 5 times, and holds the record for most sub-3:30s in a single season (6 in 2002).
Ingebrigtsen is not the youngest athlete to accomplish the feat—that distinction belongs to Noah Ngeny in ‘99, who turned 21 in November of that year.
Here is a complete list of those seasons:
Noureddine Morceli 1995 (3:27.37, 3:27.52, 3:28.37)
Hicham El Guerrouj 1997 (3:29.51, 3:29.30, 3:28.91, 3:28.92)
Hicham El Guerrouj 1998 (3:29.12, 3:26.00, 3:28.37, 3:26.45, 3:29.67)
Noah Ngeny 1999 (3:28.84, 3:29.79, 3:28.73, 3:29.19, 3:28.93)
Hicham El Guerrouj 2001 (3:28.38, 3:29.06, 3:26.12, 3:29.08)
Hicham El Guerrouj 2002 (3:29.96, 3:27.34, 3:26.89, 3:29.95, 3:26.96, 3:29.27)
Hicham El Guerrouj 2003 (3:29.76, 3:29.13, 3:28.40)
Timothy Cheruiyot 2019 (3:28.77, 3:29.97, 3:29.26)
Jakob Ingebrigtsen 2022 (3:29.47, 3:29.05, 3:29.02)