The 21-year-old prop has made 66 appearances for the Rhinos since making his debut in 2017 and was in their Challenge Cup-winning team at Wembley.
Oledzki said: “I am very happy to have agreed the new deal.
“This is the club where it all started for me and I have been here since I was 13.
“I am really grateful to everyone at this club who has helped me on my rugby journey so far and helped me progress.
“I want to stay here for as long as I can and play my best rugby. I am over the moon that we have got the deal signed.”
Leeds director of rugby Kevin Sinfield said: “It is a pleasure to be able to offer Mikolaj a new contract at the club after the hard work and dedication he has shown in recent years.
“He has been a key figure in our team this season and continues to learn and develop under Richard Agar and our coaching team.
“Importantly for the club, Mik is the fifth young player to commit their long-term future to the club.
“It shows that our development pathway is continuing to work and importantly we can give opportunities for our young players to play at the highest level.”
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