Bovine Serum Albumin (also known as BSA or "Fraction V") is a serum albumin protein derived from bovine blood. It is often used as a protein concentration standard in lab experiments. The BSA protein is purified and fractionated through a certain heat-shock procedure, followed by extensive diafiltration and ion-exchange to remove other plasma proteins, lipids, and extraneous ions.

BSA Fatty Acid-Free has extremely low levels of total lipids and fatty acids, which makes it suitable for various applications, in which lipids and fatty acids may interfere.

BSA protein has numerous biochemical applications including ELISAs (Enzyme-Linked Immunosorbent Assay), immunoblots, and immunohistochemistry. It is also used as a stabilizer and cell growth supplement in cell and microbial cultures.