Endeavour, which will be filmed in Oxford, will feature The Take star Shaun Evans in the role made famous by John Thaw.
Set in 1965, the story revolves around a hunt for a missing schoolgirl and will give viewers the chance to see where the detective's love for crosswords and classic cars came from.
It is expected to air on ITV next year.
"Morse as a young man is a wonderful character that I'm very excited to be playing," said Evans.
"My hope is that we can complement what's come before, by telling a great story and telling it well."
ITV drama commissioner Laura Mackie said the drama, titled after Morse's first name, was "a beautifully written story".
The first Morse was broadcast in 1987 with a total of 33 films made over the next 13 years.
Nearly 14 million people tuned in to watch the final episode in 2000 when novelist Colin Dexter's hero died from a heart attack.
John Thaw died of cancer in 2002 at the age of 60.
Evans has appeared in the films Being Julia and Boy A and played Nirvana lead singer Kurt Cobain in a stage play.
Inspector Morse is to return to TV screens in a one-off show about the detective's early career.