During his 15-year tenure at TfL, Ross held various roles in the press office before being appointed to the top comms job in 2008.
He was involved in numerous high-profile projects from the launch of the Congestion Charge to the integrated comms campaign for the London 2012 Olympics.
Tributes have been paid to Ross.
TfL commissioner Mike Brown said: "Stuart will be hugely missed, both as a highly distinguished public servant, and as an inspirational and warm-hearted colleague.
"He played a vital role in key moments in TfL’s history, from the aftermath of 7/7 to the huge success of the 2012 Games. He led by example – continually seeking to make our organisation reflective of the city we serve."
Vernon Everitt, managing director of customer experience, marketing and communications at TfL, said: "It is impossible to overstate Stuart’s enormous contribution to London. He joined TfL in 2000 and has been instrumental in making us the organisation we are today.
"He always put the needs of others first and has given a start in life to so many young people in the communications industry, including through a ground-breaking internship scheme.
"Stuart will always be an inspiration and hero to us and we will all miss him terribly as a colleague and friend. Our thoughts are with his family and many friends."
Paul Mylrea, a former CIPR president who was director of Media at TfL during the 2005 London bombings, said: "Stuart was one of the best people you could know. He was warm, caring and fun. But he was also someone who did the right thing. The universal praise Stuart has had from everyone he touched is a tribute to a rare individual. We will miss him dreadfully."
"Stuart was a generous and thoughtful man who faced death as he approached life — with a mix of calmness, courage, good humour and fight," Boris Johnson, the Mayor of London, told the London Evening Standard.
Ross was an annual entrant in the PRWeek Power Book. Under his leadership, TfL won the Gold Award for In-House Team of the Year at the PRWeek Awards 2015. The organisation's PR team is also a finalist in the in-house agency category for the Best Places to Work Awards 2016.
He is survived by his wife Becky and their three-year-old daughter, Rowan.