The keyboard player died at the London Clinic on Monday after suffering a fatal pulmonary embolism. The musician was "surrounded by his loving family" at the time of his death, his official website said.
Lord had announced last year that he was suffering from pancreatic cancer and would be taking a break from performing "while getting the treatment and cure."
"I shall of course be continuing to write music -- in my world it just has to be part of the therapy -- and I fully expect to be back in good shape next year," he wrote in August 2011. Born in Leicester, England, on June 9, 1941, Lord studied classical piano from a young age. He played in several jazz, blues and pop groups in the '60s.
In 1968, Lord founded Deep Purple, where he was virtually the leader of the band until 1970. He and drummer Ian Paice were the only constant band members during its existence from 1968 to 1976 and from when they reformed in 1984. He is best known for his Orchestral work 'Concerto for Group & Orchestra' which was first performed at Royal Albert Hall with Deep Purple.
Lord's solo work was universally acclaimed when he eventually retired from Deep Purple in 2002. He is survived by wife Vicky and two daughters, Amy Cherrington and Sara Lord. His first marriage to Judith Feldman ended in divorce.