Heavy chain

Heavy chain may refer to:
 * Immunoglobulin heavy chain, a subunit of antibodies
 * Heavy-chain antibody, an antibody composed of heavy chains only
 * Heavy chain disease, a disease affecting antibody heavy chain production
 * Myosin heavy chain, a subunit of myosin II
 * Myosin-heavy-chain kinase, an enzyme that catalyses the phosphorylation of myosin heavy chains