Marriner Eccles was born in Logan, Utah, on 9 September 1890, the oldest of nine children born to David and Ellen Stoddard Eccles. Marriner's father, who had migrated to Utah in 1863 at age fourteen, had become a leading industrialist, with numerous enterprises in lumber, railroads, banking, construction, livestock, sugar refineries, and food processing. Upon David's death in 1912, he left two families (and a court settlement was required on a third). Marriner, then twenty-two, took over the leadership of the businesses that were left to Ellen Eccles and her children. Marriner had worked in several of his father's businesses, had served an LDS mission in Scotland, and had attended Brigham Young College in Logan. He was a superb business analyst and bold administrator, and within eight years, through the medium of a family holding company, the Eccles Investment Company, he had acquired control of many of his father's paying enterprises.

In 1924 Marriner and his brother George, a graduate of Columbia University School of Business, joined with the Browning family in Ogden to form the Eccles-Browning Affiliated Banks, which within three years acquired control of banks at seventeen locations in Utah, Idaho, and Wyoming. In June 1928 Marriner and George Eccles and E.G. Bennett of Idaho Falls organized the First Security Corporation as a holding company to manage the seventeen banks and a savings and loan institution. This is believed to be the fist multibank holding company in the United States. Marriner, as president, was now the leading banker in the Intermountain West.

The onset of the Great Depression of the 1930s brought on a crisis in the banking industry. Under the leadership of Marriner and George Eccles, First Security withstood serious runs on its parent bank in Ogden and its bank in Boise. First Security also arranged a merger in 1932 to save the Deseret National Bank in Salt Lake City, the oldest national bank in Utah. In the process of meeting depression-caused problems, Marriner became converted to the need for a compensatory fiscal and monetary policy; he later had the opportunity of setting forth his ideas to U.S. Senators and to leaders in the administration of Franklin D. Roosevelt. He was called upon to help draft the Emergency Banking Act of 1933, the Federal Housing Act of 1934, and the 1933 act creating the Federal Deposit Insurance Corporation. In November 1934 Eccles was nominated to head the Federal Reserve System, and his appointment was ratified by the Senate in April 1935.

Marriner Eccles was the principal sponsor of the Banking Act of 1935, which restructured the Federal Reserve system into its present form. He was appointed chairman of the Board of Governors of the newly organized system in 1935 and served for seventeen years.

As an advocate of a compensatory fiscal and monetary policy, Eccles spoke before business groups, appeared on national talk shows, and gave interviews to journalists. His attempts to persuade Roosevelt were sometimes countered by Secretary Morgenthau, who was a stubborn advocate of a balanced budget, even in times of depression and recession. Eccles's talents and policies were particularly effective in countering the recession crisis of 1937-38, thus helping to build America's economic strength prior to the attack on Pearl Harbor that launched World War II.

At the end of the war, Eccles helped to lay out the agreements that created the World Bank and International Monetary Fund in 1946. He was a strong advocate of the Marshall Plan for European Reconstruction in 1948-1949; and was on the Advisory Board of the Export-Import Bank. President Harry S. Truman failed to reappoint Eccles as chairman of the Board of Governors in 1948 but retained him as vice chairman until 1951, when Marriner resigned.

Marriner resumed active participation in his family's various businesses, including First Security Corporation, Amalgamated Sugar Company, and Utah Construction Company. As the latter got into mining, it was renamed Utah Construction and Mining, still later as Utah International, Inc. Under Marriner's leadership the firm was sold to General Electric in 1976. Marriner Eccles was also active in speaking and writing about three issues that concerned him: world overpopulation; U.S. involvement in the Vietnam War; and the recognition of Red China.

Marriner founded the Marriner S. Eccles Library and Graduate Fellowship of Political Economy at the University of Utah, and the Marriner S. Eccles Foundation that has funded many charitable, scientific, and educational organizations in Utah. He was awarded an honorary doctor of laws degree from the University of Utah in 1943, and a similar degree from Utah State University in 1963. In 1982, in his honor, the Federal Reserve Building in Washington, D.C., was named for him. He died in Salt Lake City on 18 December 1977; he was eighty-seven.