Kierran Horsfield got a tattoo of the Labour leader's face below his right shoulder in November 2015, when Mr Corbyn was riding on the crest of popular grassroots support that saw him elected party leader with nearly 60% of the vote.
"I am not contemplating losing this contest, I am in it because I want to win it for the best interests of a strong Labour Party", Eagle told ITV.
"I'm not a Blairite, I'm not a Brownite, and I'm not a Corbynista".
He has refused to stand down, despite losing a vote of no confidence which saw 172 of Labour's MPs vote against him - with just 40 voting in support of their leader.
I wouldn't do this if I didn't think I had something to offer to bring our party and our country back together.
Labour's national executive committee (NEC) is expected to hold an emergency meeting this Tuesday.
New members are thought be largely supportive of Mr. Corbyn, and if he can make it on to the ballot it is likely he will be reelected.
The announcement is however in danger of being overshadowed by developments in the Conservative party leadership election.
Labour's general secretary Iain McNicol said: "I have now received sufficient nominations to trigger a contest for the position of leader of the Labour Party".
Mr Corbyn has insisted he is "ready to reach out" to his enemies in the party but warned he would stand for re-election if they tried to oust him.
"Jeremy Corbyn is unable to provide the leadership", she said.
"These are dark times for Labour and these are risky times for our country", Eagle, the party's former business spokeswoman, said on Monday in a speech in London.
Eagle has the backing of the 51 MPs needed for a formal challenge but it remains unclear whether Corbyn will also have to secure the support of MPs and MEPs in order to fight the leadership battle.
On Sunday, Corbyn said he will to sue his own party if the National Executive Commitee say he can't go on the ballot paper automatically.
After hearing the news that she would become the next Prime Minister, Mrs May said she was "honoured and humbled" to take up the top job.
In a statement to PinkNews, she said: "On 11th July 2016, I announced my decision to stand for the leadership of the Labour Party".
"I am not here for a Labour Party that just takes part. That, at a time when the country rightly is saying we need some degree of leadership form our political leaders".
"And someone who came fourth out of five to be deputy, it's not clear to me that she can win the leadership", she said on the TV show Good Morning Britain, the Independent reports.