Piquet will share a Pro/Am Oreca 07-Gibson with Andy Meyrick and Daniel Schneider, who currently race together in the LMP3 division of the Le Mans Cup series with United.
It will mark United’s first foray into the LMP2 Pro/Am subclass, which requires all crews to feature at least one bronze-rated driver.
Piquet, who won the inaugural Formula E title in 2014/15 following his brief stint with the Renault F1 team in 2008-09, last raced LMP2 machinery with Rebellion Racing back in 2017 in the FIA World Endurance Championship.
Since losing his Jaguar FE drive in 2019, he has largely focused on racing in the Stock Car Pro Series in his native Brazil.
But the 36-year-old is hoping his new tie-up with United could present the chance to contest the Le Mans 24 Hours for the first time since his final outing in the event for Rebellion in 2017.
“I’m really looking forward to be back racing in an LMP2 next year,” said Piquet. “Daniel and I have raced in the past in Brazil, getting to know each other well, so I’m excited to get the chance to race with him once more.
“It’s good to have a long-term plan set out, and I think this Pro-Am entry will allow us to have a really successful future in racing together and maybe contest a Le Mans win!”
United boss Richard Dean added: “We are delighted to announce such a strong driver line-up so early in the season.
“Daniel and Andy have worked really well together in LMP3 and they both deserve the opportunity to step into LMP2.
“Nelson’s addition to this line-up is very exciting, he is experienced and fast and will be important in our fight for another LMP2 title.”
United currently fields a single Oreca in the ELMS’ main LMP2 category for British trio Phil Hanson, Duncan Tappy and Tom Gamble, as well as a pair of Ligier JS P320s in the LMP3 class.
The Anglo-American outfit is preparing to contest Le Mans next month with its two WEC-entered Orecas.
