During a 40-year career, she hosted shows across flagship BBC stations including Radio 1, helped launch the careers of artists including Amy Winehouse and covered major music events such as Live Aid.
Her agent Nigel Forsyth said in a statement that Long died at home on Christmas Day following a short illness.
His statement said: “Janice was a wonderful, warm human being and exceptional broadcaster.
“She told a brilliant story and always made you roar with laughter with her sharp wit. She will leave behind her husband Paul and two children, who she thought the world of.
“Janice loved the BBC and started her career as a station assistant at BBC Radio Merseyside in 1979, to complete it with the magnificent people at BBC Radio Wales.
“Janice wanted it known she was so thankful to the NHS and all who looked after her there.”
Long grew up in Liverpool, the older sister of late entertainer Keith Chegwin.
After working as cabin crew and in telesales, Long started her broadcasting career as a station assistant at BBC Radio Merseyside in Liverpool in 1979.
Over 40 years she blazed a trail across Radio 1, Top Of The Pops, Radio 2 and 6 Music to name just a few
Tim Davie, BBC director-general
She became well known after joining Radio 1 in 1983, becoming the first female to have her own daily show on the station.
Long later became the first woman to be a regular presenter of Top of the Pops where she hosted the show for five years, and was one of the main presenters of the Live Aid concert in 1985.
Long was an early supporter of future stars such as The Smiths, Frankie Goes To Hollywood, Primal Scream, Adele, Amy Macdonald and Winehouse, and was awarded a BASCA gold badge of merit for her outstanding contribution to music – a forerunner of The Ivors Academy.
Since 2017, she had hosted the evening show on BBC Radio Wales.
BBC director-general Tim Davie said: “Janice Long was a stellar presenter, who was loved and respected across the industry, and her passing is a huge loss to music, broadcasting and the BBC.
“Over 40 years she blazed a trail across Radio 1, Top Of The Pops, Radio 2 and 6 Music to name just a few, before building a wonderful show and loyal following on BBC Radio Wales. She will be missed by her fans, listeners and colleagues.
“All our thoughts are with them, Janice’s family and her friends.”
Lorna Clarke, controller of pop music at the BBC, was among those paying tribute.
She said: “Everyone in pop radio was saddened to hear of the passing of Janice Long.
“She was long admired for her role as a talent spotter and new music champion, giving Frankie Goes To Hollywood and Amy Winehouse their first radio sessions, as well as lighting the way for female radio and TV presenters throughout the industry.
“We send our deepest condolences to her family and friends at this sad time.”