The FS1 host posted an incredibly emotional tribute to his 4-legged friend on Monday ... saying, "It's with tremendous sadness that I share with you my Tarzan (Tuggs, Tuggman) Sharpe has crossed over."

"What would I give, spend to have 1 more hour, day let alone a yr with the sweetest little boy ever?"

Sharpe adds his other pup, Taz, is going to miss his "big bro" ... but promises to take good care of him.

Just a few months ago, Sharpe experienced similar heartbreak -- his dog, Tonkaman, died in April after getting sick.

Sharpe reflects on all the other dogs he's lost over the years ... telling Tarzan to share his treats in doggy heaven with them.

"I will see you and all my boys again and when I do, I'll shower you all with love for the lost time."

"No more pain, suffering now go play and enjoy your new home."

Of course, Sharpe is a HUGE dog lover ... sharing moments with his pups non-stop on his social media -- from playing dress-up to taking selfies.

He also used his vacation time to cover the Westminster Kennel Club Dog Show in 2018.