Boston-based financial technology firm Circle will go public in a transaction expected to close in the fourth quarter.

Circle, which provides payments and treasury infrastructure for internet businesses, said in a statement today that it has entered into a definitive business combination agreement with Concord Acquisition Corp, a publicly traded special purpose acquisition company. The agreement calls for a new Irish holding company to acquire both Concord and Circle and become a publicly traded company. Circle is valued at $4.5 billion, according to the statement.

Circle is the principal operator of USD Coin, a dollar digital currency, which has more than $25 billion in circulation, according to the statement.

“Circle was founded with a mission to transform the global economic system through the power of digital currencies and the open internet,” Jeremy Allaire, Circle’s co-founder and CEO commented. ”We’ve made huge strides towards realizing this vision, and through this strategic transaction and ultimate public debut, we are taking an even bigger step forward, with the capital and relationships needed to build a global-scale internet financial services company that can help businesses everywhere to connect into a more open, inclusive and effective global economic system. We are thrilled to partner with Concord’s executive and investment team, drawing on their decades of operating experience growing financial services businesses around the world.”

Allaire will remain Circle’s CEO. Existing Circle shareholders will maintain approximately 86 percent ownership of the public entity. Circle said proceeds of the transaction would support product development in collaboration with the fintech firm’s initial customers.

The business combination is supported by $415 million of capital commitments from institutional investors including Marshall Wace LLP, Fidelity Management & Research Company LLC, Adage Capital Management LP, accounts advised by ARK Investment Management LLC and Third Point, the statement said.