Excess and surplus lines insurance is a segment of the insurance market that allows consumers to buy property and casualty insurance through the state regulated insurance market, where policyholders, agents, brokers and insurance companies all have the ability to design specific insurance coverages and negotiate pricing based on the risks to be secured.

"Freedom of rate and form" has given the E&S market the ability to adapt quickly to changing market conditions and those of the consumers and commercial entities seeking this unique insurance protection.The E&S originated when those who needed insurance coverage were unable to secure it from the standard carriers (or admitted carriers) due to a variety of reasons (e.g., new entity or one that does not have a adequate loss history; one that has unique coverage requirements; or a loss record that does not fit the underwriting requirements of a standard carrier).

The E&S industry is comprised of a variety of insurance companies writing what is referred to as "main street" business. The general contractor, trucking company, restaurant, bar or hotel, entities with environmental, professional liability and employment related risks and other unique exposures, are the staples of the business. A few large organizations will write the oil refineries, aircraft liability, property coverage on a communications satellite, etc.