Vivendi said it was making an offer to buy Group Bollore's 60 percent stake in advertising group Havas for 9.25 euros a share, a premium of 8.8 percent over Wednesday's closing price, in a 2.36 billion euro ($2.6 billion) deal.
The combined entity would represent more than 13 billion euros in annual revenues and add a new business to the Vivendi group, which owns Universal Music Group (UMG), one of the top three world record labels, and France's number one pay-TV Canal Plus.
The offer values Havas's total equity at 3.9 billion euros.
If Bollore's conglomerate agrees to sell its stake in the ad company, Vivendi plans to launch a simplified public tender offer on the remaining 40 percent of Havas at the same price, without seeking to delist the company, it said.
Vivendi said a merger with Havas would strongly increase its group margins but did not provide details on the potential synergies between the two groups. It said it aimed to close it by the end of June, beginning of July.
Vincent Bollore, Vivendi's chairman and controlling shareholder with a 20.65 percent stake, has pledged to turn the group into an integrated European media powerhouse and has launched a spree of acquisitions, including in Telecom Italia and Italian broadcaster Mediaset.
Havas, led by Bollore's son Yannick, was one of the two top targeted businesses in Vivendi's next expansion phase, two sources close to the matter said last month.