Season 21.
Season 1.Season 2.Season 3.Season 4.Season 5.Season 6.Season 7.Season 8.Season 9.Season 10.Season 11.Season 12.Season 13.Season 14.Season 15.Season 16.Season 17.Season 18.Season 19.Season 20.Season 21.Season 22.Season 23.Season 24.Season 25.Season 26.Season 27.Season 28.Season 29.Season 30.Season 31.Season 32.Season 33.Season 34.Season 35.Season 36.Season 37.Season 38.Season 39.
Number of episodes: 12
Synopsis:
The Challenge: Rivals is the 21st season of the MTV reality game show, The Challenge. Rivals takes place in Costa Rica, Argentina, and Patagonia. The season used former cast members from The Real World and The Challenge. Rivals marked the first season of The Challenge to not include any cast members from cancelled series Road Rules. The season featured an incendiary format in which players were teamed with their arch enemies from past seasons of The Real World and The Challenge. The season premiered on June 22, 2011
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Episode 1.
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Episode 2.
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Episode 3.
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Episode 4.
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Episode 5.
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Episode 6.
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Episode 7.
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Episode 8.
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Episode 9.
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Episode 10.
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Episode 11.Reunion
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Episode 12.The S#!@ They Should Have Shown
Noah's Ark 
The Bourne Identity 
Taffy 
First Kill 