* Weight? In that case, the Mandrill is the largest monkey, weighing up to 82 pounds!
* Height? The Eastern Lowland Gorilla is the largest, reaching up to 6 feet tall when standing on all fours.
* Length? Again, the Eastern Lowland Gorilla wins, measuring up to 6.5 feet in length.
However, it's important to remember that gorillas are actually classified as apes, not monkeys. If you're specifically asking about monkeys, then the Mandrill takes the top spot in both weight and length.
So, to be precise:
* Heaviest monkey: Mandrill (up to 82 pounds)
* Tallest monkey: Mandrill (up to 3 feet tall when standing)
* Longest monkey: Mandrill (up to 4 feet long)