The Scottish actor will play the iconic Jedi Master in the limited series, which will launch on Disney+ on May 25 this year.
It will be based 10 years after the dramatic events of Star Wars: Revenge of the Sith.
The 2005 film saw Obi-Wan Kenobi face his greatest ever defeat as his Jedi apprentice Anakin Skywalker turned to the dark side as evil Sith Lord Darth Vader.
McGregor, 50, will join a star-studded cast, which will also see Hayden Christensen in the role of Vader.
Other names on the case include the likes of Moses Ingram, Joel Edgerton and Benny Safdie.
Ewan has previously said that the new series will “satisfy” die-hard Star Wars fans.
He told Forbes: “I always felt there was a story between Episode III where I finished playing Obi-Wan in the movies and Episode IV where Alec Guinness is Obi-Wan Kenobi.
“The [Obi-Wan Kenobi series] writers and Deb and I and everyone, I think we crafted or they crafted a very fine storyline. I think people are going to like it.”
“We finished shooting our series, and it was really, really good fun – I really enjoyed working with [director] Deborah Chow,” he said.
“I think it will not disappoint,” he added. “I think it’s gonna be good. I had a really good time making it, and worked with some really wonderful people, lovely people.
“The new technology we employed doing it is cool, and it was a different experience than making the original three films that I did.”
There could be some surprises in store as well as McGregor dropped a big hint in conversation with chat show host Jimmy Kimmel.
“I got to play a very special scene on May 4th with someone very special in my life, and that’s all I can tell you about it,” he said in an interview from earlier this year.
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