Alanine (abbreviated as Ala or A) is an α-amino acid with the chemical formula CH₃CH(NH₂)COOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid. L-Alanine is second only to leucine in rate of occurrence, accounting for 7.8% of the primary structure in a sample of 1,150 proteins.D-Alanine occurs in bacterial cell walls and in some peptide antibiotics.

The α-carbon atom of alanine is bound with a methyl group (-CH₃), making it one of the simplest α-amino acids with respect to molecular structure and also resulting in alanine's being classified as an aliphatic amino acid. The methyl group of alanine is non-reactive and is thus almost never directly involved in protein function.

Alanine is a nonessential amino acid, meaning it can be manufactured by the human body, and does not need to be obtained directly through the diet. Alanine is found in a wide variety of foods, but is particularly concentrated in meats.

Roger Meredith Harris (born July 27, 1933, Otahuhu, Auckland) is a former New Zealand cricketer who played in 2 Tests in 1959.