12:58 PM PT -- Francis Ngannou released a statement on the loss ... and it's incredibly emotional.

"Too soon to leave but yet he's gone," he said. "My little boy, my mate, my partner Kobe was full of life and joy. Now, he's laying without life. I shouted his name over and over but he's not responding."

Ngannou added Kobe made him his "best self" ... and he's now lost without him.

"Life is so unfair to hit us where it hurts the most."

Ngannou ended the statement by asking his followers to give advice on how to heal ... because right now, he doesn't know how to move forward.

Combat sports superstar Francis Ngannou is mourning the tragic passing of his 15-month-old son this week ... expressing his heartbreaking grief on social media.

"What's the purpose of life if what we're fighting tooth and nail to get away from is what finally hit us the hardest!?" Ngannou posted on X on Monday. "Why is life so unfair and merciless?"

"Why does life always take what we don't have? I'm f***ing tired."

Details surrounding his son's death were not revealed ... although those close to "The Predator" asked for privacy during the unbelievably challenging time for his family.

The fighting community is now rallying behind the former UFC heavyweight champion ... including Conor McGregor, who shared kind words for Ngannou.

"I am so sorry to hear of your loss Francis," McGregor said. "My prayers are with you and your family at this time."

Cris Cyborg added a touching prayer ... saying, "Dear lord, I pray you comfort Francis and his family. Surround him with your love and ensure he is protected by your guidance as he grieves this loss."

"Give him the strength to know that heaven is eternal and they will be together soon as this life is just a blink of an eye."