Fitch made the announcement after the market closed.
It affirmed its "BBB+" investment-grade rating on about $8.6 billion in debt for Houston-based Marathon Oil. The rating is three notches above junk. The ratings company said its decision was based on concerns about lower commodity prices and margins as well as Marathon Oil's sizable multiyear investment program.
Fitch Ratings revised its ratings outlook to "Stable" from "Negative," noting Marathon Oil has made progress on asset sales, the proceeds from which will provide a liquidity buffer in case of another drop in commodity prices.
Shares of Marathon Oil rose 7 cents to close Monday at $31.91.
