Price comparison website Gocompare.com, which is based in Newport, is being taken over by insurance company Esure in a deal worth £95m.
The company's founder and chief executive Hayley Parsons will stand down as part of the deal, which needs to be approved by regulators.
Ms Parsons started the business eight years ago. Gocompare will continue to be run from its current headquarters.
Esure already owns 50% of Gocompare after buying into the company in 2010.
The sale values Ms Parson's remaining 23% stake at almost £44m.
The deal gives Gocompare a total valuation of £190m.
Ms Parsons said: "I am very proud that a company I started at my kitchen table eight years ago has achieved so much in such a short period of time.
"Today, we are a leading price comparison business in the UK and this is credit to all the wonderful, hard-working people we have in Newport."
The company became well-known for its advertising featuring a fictional Italian tenor called Gio Compario.
Hayley Parsons profile
Hayley Parsons, 41, spent 14 years working at Admiral insurance in Cardiff after joining them straight from school.
She became head of business development and was one of the founders of their price comparison site Confused.com, the first car insurance comparison site in the UK.
She left in 2006 to set up Gocompare, which she wanted to focus on the levels of cover provided by a particular insurance product rather than just the cost.
Ms Parsons won several awards in the following years, including Welsh Woman in Innovation in 2008, Woman in Business from the South Wales Chamber of Commerce Business Awards in 2009, and the business leader category in the Inspire Wales Awards in 2010.
In 2012, she was awarded an OBE for services to the economy.