The hard-living heavy rock legend has battled serious health issues in recent years, forcing him to scale back on his fabled alcohol intake and prompting his band to reschedule concert dates.
But he recently urged fans to stop worrying about him, insisting he was doing fine.
He told Classic Rock, "I'm sick of the f**king, 'Are you going to die?' line of questioning. It's getting really old, that question. I’m alright. I'm going out there and doing my best. I have good days and bad days but mostly I've been doing alright. The last tour of the States was very good."
Lemmy's manager confirmed the news the rocker had died on Monday afternoon (28Dec15), revealing the Ace of Spades singer learned he was battling cancer just days before his death.
A post on the band's Facebook page reads: "There is no easy way to say this… our mighty, noble friend Lemmy passed away today after a short battle with an extremely aggressive cancer.
"He had learnt of the disease on December 26th, and was at home, sitting in front of his favorite video game from the Rainbow (bar in Los Angeles) which had recently made it's way down the street, with his family. We cannot begin to express our shock and sadness, there aren’t words. We will say more in the coming days, but for now, please… play Motorhead loud."
In addition to cancer, Lemmy had been suffering from hematoma and was fitted with a defibrillator to correct an irregular heartbeat in 2013.
Born Ian Fraser Kilmister in Staffordshire, England in 1945, Lemmy once served as a roadie to the Jimi Hendrix Experience. After spending much of his youth playing in a number of bands, he joined rockers Hawkwind in 1972, becoming the British band's singer and bassist. He was fired from the group following a drug possession arrest during a North American tour.
He co-founded Motorhead in 1975 and appeared on all the trio's 20 studio albums.
Truly influential, the band inspired hard rock supergroups Metallica, Guns N’ Roses and Foo Fighters, among others, with many of today's leaders of the genre naming Lemmy among their heroes.
A true hard-living rock icon, he once claimed he had guzzled a bottle of Jack Daniel's bourbon every day since turning 30. In recent years, poor health forced him to cut back on his boozing and he recently confessed he had swapped whiskey for the occasional glass of red wine.
"Apparently I am still indestructible," he told The Guardian last year (14).
Paying tribute to his fellow heavy rock legend, Ozzy Osbourne was among the first stars to offer his thoughts on Lemmy's passing. He took to Twitter on Monday evening (28Dec15) and wrote, "Lost one of my best friends, Lemmy, today. He will be sadly missed. He was a warrior and a legend. I will see you on the other side."
Lemmy's death comes a month after the passing of original Motorhead drummer Phil Taylor, who died on 11 November (15), aged 61.