* State Farm: Often cited as the largest auto insurer in the US by market share and number of policies.
* Geico: Known for its extensive advertising and competitive pricing, consistently ranking among the top insurers.
* Progressive: Another major player, known for its online tools and personalized insurance options.
* Allstate: A long-established company with a wide range of insurance products.
* Liberty Mutual: A large national insurer with a significant market share.
Other companies that frequently appear in discussions of leading insurers include USAA (primarily serving military members and their families), Nationwide, and Farmers Insurance. The specific ranking can fluctuate slightly from year to year based on different data sources.