The pyramidalis muscle is a small triangular muscle, anterior to the rectus abdominis muscle, and contained in the rectus sheath.

The pyramidalis muscle is part of the anterior abdominal wall. Inferiorly, the pyramidalis muscle attaches to the pelvis in two places: the pubic symphysis and pubic crest, arising by tendinous fibers from the anterior part of the pubis and the anterior pubic ligament.

Superiorly, the fleshy portion of the pyramidalis muscle passes upward, diminishing in size as it ascends, and ends by a pointed extremity which is inserted into the linea alba, midway between the umbilicus and pubis.^{[citation needed]}

The pyramidalis muscle is innervated by the ventral portion of T12.

The pyramidalis is most commonly supplied by a separate branch of the inferior epigastric artery, but it may also be supplied by the superior epigastric artery in few cases. It is drained by the respective named veins.

The pyramidalis muscle is present in 80% of human population.^{[unreliable source?]} It may be absent on one or both sides; the lower end of the rectus then becomes proportionately increased in size.

Occasionally, it is doubled on one side, and the muscles of the two sides are sometimes of unequal size.^{[citation needed]} It may also extend higher than the usual level.^{[citation needed]}

The pyramidalis muscle tenses the linea alba when contracting.^{[citation needed]}