A Credit Rating Agency is a company that assesses and assigns credit ratings to issuers of debt securities, including governments and corporations. The three major agencies are Standard & Poor's (S&P), Moody's, and Fitch Ratings, whose downgrades or upgrades can significantly move financial markets. These agencies use proprietary methodologies to evaluate creditworthiness and play a critical role in determining the interest rates that borrowers pay.
Example
“The three major credit rating agencies — S&P, Moody's, and Fitch — assigned different ratings to a new government bond issue, with S&P rating it AA while Moody's gave it Aa2, reflecting their slightly different assessment methodologies.”