Ralphs last performed with the rockers in October 2016, before he suffered a stroke a month later.
A statement from singer Rodgers on the website said: 'Our Mick has passed, my heart just hit the ground. He has left us with exceptional songs and memories.
'He was my friend, my songwriting partner, an amazing and versatile guitarist who had the greatest sense of humour.
'Our last conversation a few days ago we shared a laugh but it won't be our last. There are many memories of Mick that will create laughter. Condolences to everyone who loved him especially his one true love, Susie. I will see you in heaven.'
Drummer Kirke said: 'He was a dear friend, a wonderful songwriter, and an exceptional guitarist. We will miss him deeply.'
Bad Company was formed in 1973 after the members of the bands Free, Mott The Hoople and King Crimson joined forces.
Ralphs is set to become a member of the Rock & Roll Hall of Fame as a member of Bad Company in November.
“Our Mick has passed, my heart just hit the ground," Bad Company singer Paul Rodgers said in a statement. “He has left us with exceptional songs and memories. He was my friend, my songwriting partner, an amazing and versatile guitarist who had the greatest sense of humour.”
Ralphs wrote the 1970's song “Ready for Love” for Mott the Hoople, later revamped for Bad Company's 1974 debut album, which also included the Ralphs-penned hit “Can't Get Enough.” He co-wrote Bad Company's 1975 classic “Feel Like Makin' Love” with Rodgers.
