The chief executive of Exxon Mobil Corporation, Lee Raymond, will retire at the end of 2005, ending a 12-year reign in which he built a Standard Oil Trust successor into the world’s largest publicly traded company.

The company’s president, 53-year-old Rex Tillerson, probably will succeed the 66-year-old Mr. Raymond as chairman and chief executive, Exxon Mobil said yesterday in a statement. At the board’s request, Mr. Raymond became the first chief since 1933 to work past the company’s mandatory retirement age of 65. Exxon Mobil, based in Irving,Texas, has a cash balance that more than tripled in the past two years to $30 billion.

“Lee Raymond is one of the great men of the industry, and I have unabashed admiration for him,” Donald Coxe, who manages $21 billion including Exxon Mobil shares at Harris Investment Bank, said. “The challenge facing his successor will be to find enough big projects in which to invest their billions.”

Mr. Raymond led the former Exxon Corporation’s 1999 purchase of Mobil Corporation for $85.2 billion, the biggest oil acquisition in history.

Exxon Mobil last week posted the highest second-quarter profit in its 123-year existence and had the most revenue on record for any public company.

Mr. Raymond “orchestrated the development of the modern global energy company,” a former Exxon Mobil geologist who helps manage $36 billion at Wilmington Trust Company, Gene Pisasale,said.”He engineered the most successful merger in energy-sector history and one of the most successful in the history of corporate America.”

Since Mr. Raymond was named chief executive in April 1993, Exxon Mobil’s shares have risen an average of 14% annually, including reinvestment of dividends. That compares with an 11% average for Standard & Poor’s 500 members.

Mr. Raymond, a University of Minnesota-trained chemical engineer, joined the company in 1963 as a researcher.

Before being promoted to president last year and emerging as the leading candidate to replace Mr. Raymond, Mr. Tillerson managed some of Exxon Mobil’s biggest projects and handled some of its most delicate negotiations. He joined the company in 1975.

Mr. Tillerson has helped run such projects as Chayvo, an offshore field near Russia’s Sakhalin Island that has the world’s most powerful drilling rig. Exxon Mobil is counting on multi-billion-dollar developments in such places as Russia and West Africa to make up for slowing output at old American fields.

The choice of Mr. Tillerson to succeed Mr. Raymond was expected, an analyst at Sanford C. Bernstein in London who rates Exxon Mobil shares at outperform and doesn’t own any, Neil McMahon, said.

“This has been telegraphed for the past year,” he said.

Shares of Exxon Mobil fell 48 cents to $58.52 in New York Stock Exchange composite trading. The stock still has climbed 14% this year.

The company has its roots in John D. Rockefeller’s Standard Oil Trust of the 1880s, when kerosene began to displace whale oil as household lighting fuel.The company changed its name to Exxon Corporation in 1972 and later bought Mobil, formerly known as Standard Oil of New York.