The combined company will generate nearly €170 billion ($189 billion) annually, which is projected to be the third-most revenue of any automaker — leapfrogging GM, Ford and other companies.
Gamble, 64, will serve the remainder of the term of former head Gary Jones, who has been implicated in a federal embezzlement and bribery scheme at the union and resigned his post last month.
Jones has been the target of a federal probe of alleged corruption in the UAW. The union is also linked to an alleged bribery scheme, according to a lawsuit filed by GM against rival Fiat Chrysler.
The new company, with combined annual revenue of $189 billion, would be based in the Netherlands and control such brands as Dodge, Ram, Citroën and Opel.
Fiat Chrysler will pay more than $500 million to resolve Justice Department lawsuits over claims it used illegal software to allow 104,000 diesel vehicles to skirt emissions guidelines.
Sergio Marchionne, the man who saved Fiat Chrysler, has died. His successor now leads a company facing big challenges. It has yet to crack the key Chinese market and tariffs may hurt profits.
The Chinese company Great Wall Motor has expressed interest in acquiring the Jeep brand from Fiat Chrysler Automobiles. Sales of Jeep and other U.S. brands have been growing in China.
The Environmental Protection Agency says Fiat Chrysler violated the Clean Air Act by allegedly installing software in about 104,000 vehicles that masked the true level of emissions.
The automaker confirmed the Securities and Exchange Commission is asking questions, along with the Justice Department, about the accuracy of reports the company files on its car sales.
This is the first time Google has worked directly with an automaker to integrate its self-driving technology into a passenger vehicle, the companies said in a joint statement.
The UAW announced the agreement just after Wednesday's strike deadline of 11:59 p.m. Fiat Chrysler is the first of Detroit's big three automakers to reach a tentative contract with the UAW.
If the United Automobile Workers union does strike, it would be the first against a Detroit automaker in eight years. Workers previously rejected a deal presented by union leadership and management.
Observers were surprised when Fiat Chrysler was selected as the first of Detroit's automakers to negotiate an agreement, or serve as a "strike target."
The automaker admits it failed to promptly and effectively recall vehicles with defects, including ones that could cause drivers to lose control. The company will also buy back some cars from owners.
