The rectus abdominis muscle (commonly known as "abs") is a paired muscle running vertically on each side of the anterior wall of the human abdomen (and in some other animals). There are two parallel muscles, separated by a band of connective tissue called the linea alba (white line). It extends from the pubic symphysis/pubic crest inferiorly to the xiphisternum/xiphoid process and lower costal cartilages (5-7) superiorly.

It is contained in the Rectus sheath.

The rectus is crossed by three fibrous bands called the tendinous inscriptions. Colloqiual names for the appearance of a well-defined rectus abdominis include a "six pack" and "washboard abs".