The Starfish Project is a UK-based not-for-profit therapy programme which helps people who stammer or stutter to overcome their speech disfluencies through the use of diaphragmatic breathing (also known as costal breathing). The programme also teaches participants to reassess negative emotions surrounding their stammering through the use of avoidance reduction therapy, a form of stuttering modification (see stuttering therapy).

Students attend a three-day residential course during which a diaphragmatic breathing technique and non-avoidance strategies are taught. Following on from this initial course graduates are able to attend additional 'follow-up' courses without charge as often as they feel necessary. Graduates are also encouraged to make use of a list of phone contacts and can attend monthly support meetings at various locations around the UK.

Although diaphragmatic or costal breathing can be an effective way for stammerers to manage their condition, it should not be regarded as a cure. In addition to the Starfish Project, a similar breathing technique is used by other stammering treatment initiatives including the McGuire Programme.