American company providing online personal-relationship and matchmaking services. Founded in 2000 by Neil Clark Warren, a clinical psychologist, eHarmony is based in Pasadena, Calif. The company aims to unite compatible individuals in long-term relationships via scientific methods.

After signing up with the service, a user completes a lengthy survey designed to evaluate his or her emotional health, values, beliefs, characteristics, and skills. From the survey, a personality profile of the user is created, as well as a compatibility profile, which describes the type of person for whom the user is ideally suited. Once the survey and profiles have been completed, eHarmony attempts to match the applicant with a suitable partner using a patented matching system. This system was developed by the company after researching 5,000 married couples and identifying the factors that make marriages succeed or fail. Once a list of partners is produced, eHarmony assists the user in narrowing the list and making initial contact.

Unlike competing matchmaking services, eHarmony does not allow users to browse through profiles of potential partners; they must rely on the company to make selections for them. Individuals who are already married, have had four or more previous failed marriages that resulted in divorce, are seeking a same-sex partner, suffer from severe depression, or are under age 21 are not eligible to participate in the company's matchmaking service.

In 2006 eHarmony launched a new service for already-married couples looking to strengthen their relationship or overcome challenges.