The present disclosure relates to antigen binding proteins, such as antibodies, that bind to HER3, polynucleotides encoding such antigen binding proteins, pharmaceutical compositions comprising said antigen binding proteins and methods of manufacture. The present disclosure also concerns the use of such antigen binding proteins in the treatment or prophylaxis of diseases associated with breast cancer, ovarian cancer, prostate cancer, bladder cancer, pancreatic, gastric, melanoma and other cancers that overexpress HER3.