Mary L. Schapiro, who overhauled the Securities and Exchange Commission after the financial crisis, announced Monday that she is stepping down as chairwoman of the agency.

In recent days, the SEC informed the White House and Treasury Department that Schapiro planned to leave Dec. 14, becoming the first major departure from the Obama administration’s team of financial regulators. Schapiro will also relinquish her position as one of the five members of the agency’s commission, the group that oversees Wall Street and the broader financial markets.