Erin go brew.

Much Guinness will flow today, but even when it’s not St. Patrick’s Day, the storied Irish stout is New York’s second most popular beer, a study has found.

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The city’s top three favorite beers are Samuel Adams, Guinness and Corona, market research firm BrandIndex told The Post.

Samuel Adams was also ranked No. 1 nationally, according to the survey, which analyzes brand image and not necessarily sales.