Rivers United emerged in 2016 from a merger of two traditional Port Harcourt-based sides, Sharks and Dolphins, two football clubs owned by Rivers state. Official records however show that the club inherited the slot of Dolphins FC as the club then known as Sharks were relegated from the Nigeria Professional Football League (NPFL) at the end of the 2015 season. As Dolphins FC, the club won the Nigerian league in 2004 and 2011 with Coaches Musa Abdullahi (Late) and Stanley Eguma (incumbent) respectively. It also won the Nigerian FA Cup in 2001, 2004, 2006 and 2007.

Dolphins FC also reached the final of the 2005 CAF Confederation Cup but lost 1-3 on aggregate to Moroccan side FAR Rabat. Rivers United finished second in 2016 behind Rangers International to earn their first CAF Champions League ticket and were placed 3rd in the 2019/20 NPFL season which though was called off after MatchDay 25 in the wake of the COVID 19 pandemic that forced countries to shut down sports.

That will see them competing in the 2020/21 CAF Confederation Cup. Rivers United has had a fair cast of famous Nigerian players including Victor Ezeji who holds the record of enjoying the longest career spell of 20 years in the NPFL.

Others are Sunday Rotimi, a former Super Eagles goalkeeper, Kelechi Osunwa, a junior international who also had brief calls to the Super Eagles and former long term captain, Ahmed Abdulrahman. After playing at the Yakubu Gowon Stadium for 20 years from its era as Dolphins, Rivers United has announced it would relocate to the more modern Adokiye Amiesimaka Stadium in Igwuruta-Ali