The electoral council said the president of the Citizens Alliance for Liberty Party (CXL) holds dual US and Nicaraguan citizenship in violation of the law.
President Daniel Ortega has been accused of silencing the opposition.
Earlier on Friday, the US imposed visa restrictions on dozens of Nicaraguans linked to the government.
Nicaragua’s supreme electoral council accused CXL of carrying out “verbal acts that undermine independence, sovereignty and auto-determination”.
The electoral council, which is tied to the ruling party, also revoked the citizenship of CXL’s leader Carmella Rogers Amburn, also known as Kitty Monterrey, leaving her at risk of deportation.
It comes just days after a former beauty queen was arrested after registering as an opposition candidate. Authorities charged Berenice Quezada, who was crowned Miss Nicaragua in 2017, with inciting terrorism and she was released pending trial.
Opposition to Mr Ortega, who is currently in his fourth term in office, three of them consecutive, has been growing in the past years.
In 2018, mass anti-government protests swept through the country but were met with a violent police response. Hundreds were killed and thousands were injured in the clashes between the protesters on the one hand, and the security forces and pro-government militia on the other.
After many of those who had lead the demonstrations were arrested, the protests eventually fizzled out later that year.
Mr Ortega rejected calls made at the time for elections to be brought forward and continued to serve his term.
But critics say that with the scheduled date of the presidential poll approaching – they are due to be held in November 2021 – he is now targeting anyone who may stand against him.