The Northwestern Mutual Life Insurance Company is a major financial services company based in Milwaukee, Wisconsin. Founded in 1857, it is one of the largest providers of life insurance in the United States.

Its products are offered exclusively through a captive sales force of approximately 7,500 financial representatives known and marketed as the "Northwestern Mutual Financial Network". The company has consistently been named "America's Most Admired" life/health insurance company by Fortune Magazine for the last 23 years.

Unlike many other major U.S. life insurers, notably Metropolitan Life and Prudential, it has retained the mutual form of business organization where the company is owned by its policyowners and there are no shares. This arrangement has become increasingly rare among North American life insurers as capital for growth must be generated internally rather than through the sale of additional equity to investors. Mutual insurers are by definition nonprofit organizations; monies raised above those needed to pay claims, provide for overhead expenses, and allow for reasonable growth are returned to the holders of "participating" policies in the form of dividends. These dividends reduce the cost of insurance and give Northwestern a distinct competitive advantage.

For many years, Northwestern Mutual did not engage in advertising. Its campaigns of recent years referring to it as "The Quiet Company" are meant to emphasize that fact. Northwestern is generally very highly rated by analysts of insurance companies and their business practices such as A.M. Best.

Northestern Mutual has invested its clients' monies in many diverse ways over the years, sometimes in investments not traditionally associated with insurance companies. One of the best-known such investments was the ill-fated Great Lakes ore carrier the SS Edmund Fitzgerald.