Albumin refers to any of a group of proteins soluble in water and 50% saturated ammonium sulfate solution. Albumins (albumens) are present in both animals and plants. Ovalbumin is the chief protein in egg white; serum albumin occurs in blood plasma, where it controls osmotic pressure.

Albuminuria is the presence of serum albumin in the urine. It may result from eating certain types of foods, or from certain diseases, notably those of the kidney.