There are many species of Monitor lizard. Most of them can grow “very big”.
I own a 3 years old female Savannah monitor and 2 baby Asian Water monitors.
The Savannah monitor (Varanus Exanthematicus) is a medium-sized Monitor lizard that is native to Africa. They are also known as the Bosc’s monitor in Europe.
The Varanus Salvator is also commonly known as the Asian Water monitor. It is a large varanid lizard native to South and Southeast Asia.