The deal, subject to shareholder approval, marks the second transatlantic stock market alliance in two months, following the acquisition of the main European market Euronext by the New York Stock Exchange.
The acquisition is a major breakthrough for the Nasdaq, which still owns almost 30 percent of the London exchange and could use the purchase of OMX to persuade LSE shareholders to agree to a deal creating a giant European exchange.
Nasdaq Chief Executive Robert Greifeld said, ”The future of exchanges is about technology, flexibility and scale ... Nasdaq and OMX together deliver all of these benefits.”
The price of shares in OMX leapt by 14.33 percent in early Friday trading.
The group owns stock exchanges in Copenhagen, Stockholm, Helsinki, Reykjavik, Riga, Tallinn and Vilnius.