A message on the band's official website said Ralphs is "survived by the love of his life, Susie Chavasse, his two children, three step-children", as well as his bandmates Paul Rodgers and Simon Kirke.
Bad Company was formed in 1973 after the members of the bands Free, Mott The Hoople and King Crimson joined forces.
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."
Ralphs' final performance with Bad Company was in October 2016, with the musician suffering a stroke the following month.
Free members Rodgers and Kirke had enjoyed success with their 1970s hit song All Right Now.
Ralphs had been part of Mott The Hoople, famed for their 1972 song All The Young Dudes, which was penned by David Bowie.
Vocalist and guitarist Raymond 'Boz' Burrell had been performing as part of rock band King Crimson.
Bad Company are due to be inducted into the Rock and Roll Hall of Fame later this year.
The group rose to fame in 1974 with their self-titled debut album which included hits such as Can't Get Enough and Movin' On.
The album reached number three in the UK albums chart and went five-times platinum.
Bad Company later released Straight Shooter in 1975, followed by Run With The Pack, and both made it into the top five in the albums chart.
They were also known for rock anthems including Ready For Love, Rock Steady and the title track Bad Company.
Among those paying tribute to the late guitarist was Joe Elliott, lead singer of the hard rock band Def Leppard, who shared a post on the group's X account saying: "I just heard the news ... totally heartbroken ... Mick has been a constant companion through my musical journey & he was one of the kindest souls I ever met. The world is a poorer place today."
David Coverdale, lead singer of Deep Purple and then Whitesnake, said on X: "Heartbreaking News...Loved Mick ...Sweet, Sweet Man & Super Songwriter...My Sincere Condolences To His Family, Friends & Fans."
In another post, he added: "Mick Ralphs was the first person I played the original song idea to Love Ain't No Stranger before I played it to the band...he was super encouraging...A total sweetheart."
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