Einar Lundsgaard (12 February 1899 – 18 December 1968) was a Danish professor of physiology at the University of Copenhagen (1934–1967).
He was among the first to demonstrate that muscles contractions drew their energy from dephosphorylization of creatine phosphate when glycolysis was inhibited using iodoacetate.
Lundsgaard was born in Copenhagen where his father was a physician who came from the Gundelach family of lawyers and civil servants His father received a gold medal for his work on prostatic hypertrophy from the University of Copenhagen.
He completed studies in 1923 and worked at the institute of medical physiology under Valdemar Henriques.
Creatine phosphate was independently identified in muscle by the Eggletons and by Cyrus H. Fiske and Subbarow in 1926.