32-year-old Struve -- known as "The Skyscraper" -- has been fighting in the UFC since 2009, and famously beat current UFC heavyweight champ Stipe Miocic in 2012.

But, the giant from the Netherlands has decided to hang up gloves after dealing with vertigo, hearing loss and other issues.

"I was contacted by the UFC last week for a fight," Struve said ... "However, I’ve decided it’s my time to retire from fighting."

"I’ve had an inner ear issue that I’ve been battling since May [of] last year. I caught a viral infection that has damaged my vestibular system and the hearing nerve in my right ear."

Struve says his doctors expected him to make a full recovery -- during his fight against Tai Tuivasa in October 2020, he got flush on his right ear, which made everything worse.

"After that fight I was having more issues again and the doctor scheduled new tests," Struve explains.

"After these tests I was told the damage in my ear and the vestibular issues caused by the viral infection I’ve been dealing with are mostly permanent."

Struve says he has "no big issues" when living his everyday normal life ... it's only when he trains hard that his medical issues flare up and cause serious discomfort.

"The extreme intensity I have put my body through and training camp to get ready for fights I can’t do anymore."

"At this juncture I realize that it’s time to hang up the gloves for good, and put my health and family first."

Struve says the fact he has a 5-month-old child is also a factor in his decision -- he wants to be able to focus on being a good father.

He may not have been the greatest fight in the UFC, but he was always fun to watch. Congrats on a pretty amazing career.