Exxon Mobil Corp. recruited a company outsider for the first time to join the CEO's inner circle of managers, a move that comes just weeks after the oil giant suffered a stunning setback at the hands of a tiny activist investor.

Kathryn Mikells will join Exxon on August 9 as CFO from Diageo Plc, where she held the same role and was also a director, according to a statement Monday. Mikells, 55, will be the first woman among the ranks of senior vice presidents who share day-to-day management duties with CEO Darren Woods, and the first executive to hold such a high position without a background in oil, natural gas, or chemicals.

The decision to appoint Mikells, whose previous experience included stints at Xerox Corp., ADT, and United Airlines Holdings Inc., comes after Engine No. 1 took control of 25 percent of Exxon's board last month. Though the activist investor urged the company to address climate concerns and improve its financial performance, it didn't target the CFO role or call for more diversity among senior executives. Mikells will replace retiring senior vice president Andrew Swiger.