The show, which is set in a women's prison, was one of the streaming service's first original shows and one of their biggest hits.
But they have revealed that it will finish after the upcoming seventh and final series.
OITNB's official Twitter account broke the news with an announcement saying: "Warning: This may make you cry. The Final Season, 2019", accompanied by a video with cast members including Taylor Schilling, Uzo Aduba, Laura Prepon and Dascha Polanco.
As well as saying goodbye to the long-running programme, they also promised it would go out with a bang.
ONITB first hit our screens in 2013 and has scooped a host of awards, including Emmys and Screen Actors Guild gongs.
The show is set in the fictional Litchfield prison and is based on the 2010 memoir, Orange Is The New Black: My Year In A Women's Prison, by Piper Kerman.
Uzo, who plays Suzanne "Crazy Eyes" Warren, said: "Season seven, you will not be disappointed.
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"It is a season you will not forget and we are going to give you everything and more that you could have ever wanted."
"I'm so grateful for the fun times, the knowledge, the friendships, the love, the family that we have created together," she added.
Kate Mulgrew, who plays Galina "Red" Reznikov, added: "I'm going to miss playing and living on the edge of one of the most groundbreaking, original and controversial series of this decade."
Series six ended with Piper being released from prison early, hinting she would write a book of her own experiences of prison.
Meanwhile, show creator, Piper Kerman, who Piper Chapman is based on, added: "After seven seasons, it’s time to be released from prison. I will miss all the badass ladies of Litchfield and the incredible crew we’ve worked with. My heart is orange but… fade to black."