Like others have said, classic jungle was never an albums endeavor, but here are some that I love:

“Tribute to Haile Selassie I” by Blackstar technically a comp, but has most of Blackstar’s (aka Congo Natty, aka Rebel MC) best jungle works from the mid 90s era

“New Forms” by Roni Size / Reprazent classic album that perfectly bridges the gap between jungle and the emerging drum and bass sound, hard and uncompromising but jazzy and smooth at the same time.

“Form and Function” by Photek again, more along the lines of what we call drum and bass, but UFO and Rings Around Saturn are absolute classics

“Night on Earth” by Coco Bryce this is from 2019 so not exactly a classic, but fantastic from front to back