At a time when investors are nervous and antitrust regulators are suspicious, the prospect of a $100 billion-plus merger on the horizon may seem remote.

Yet in a bold step toward creating a global colossus in beer, Anheuser-Busch InBev said on Wednesday that it had approached its rival SABMiller about a potential takeover.

If successful, a merger of the companies, the world’s biggest brewers, would put some of the most popular beers under one roof: Anheuser-Busch InBev’s Budweiser, Corona and Stella Artois would join Miller Lite, Peroni and Grolsch from SABMiller.

Combined, the companies would have $69 billion in annual revenue and command of 30 percent of global beer sales, according to the research firms Euromonitor International and IBISWorld.