The 26-year-old from Helensburgh in Scotland came off just after the 28th Milestone on the third lap.
A statement issued by the organisers said: ‘ACU Events Ltd regrets to confirm that Adam Lyon, 26, from Helensburgh in Scotland was killed in an incident during the Supersport 1 Race today at the Isle of Man TT Races.
The accident occurred at Casey’s, just after the 28th mile of the course, on the 3rd lap of the race.
‘Adam was a newcomer to the TT this year. He qualified in 24th place for today’s race with a fastest lap of 122.261 which he improved to 122.636mph on the opening lap of today’s race. His fastest lap of the TT course – 123.443 - was in Friday’s Superbike qualifying session.
‘Adam lapped at 122.499 as a newcomer at the Ulster Grand Prix in 2017, finishing 11thin the second Supersport race. He finished sixth in the 2010 Pirelli National Superstock 600 Championship with podiums at Croft and Silverstone.
‘ACU Events Ltd wishes to pass on their deepest sympathy to Adam’s family and friends’.
Mr Lyon is the second rider killed at the event this year after Manxman Dan Kneen lost his life following a crash in practice last Wednesday.
This story first featured on our sister title the Belfast Newsletter.