This review by S. Viguet-Carrin, P. Garnero, and P.D. Delmas explores the role of collagen in bone strength. Bone strength is influenced by both the quantity and quality of bone tissue, with the latter characterized by geometry, microarchitecture, turnover, mineral content, and collagen. The review highlights the interplay between type I collagen and minerals, emphasizing the importance of collagen fiber orientation under mechanical forces. It discusses various maturation processes of collagen, including enzymatic and nonenzymatic modifications, such as the formation of crosslinks by lysyl oxidase and the accumulation of advanced glycation end products. These modifications can affect bone strength and are associated with conditions like osteogenesis imperfecta and osteoporosis. The synthesis and structure of type I collagen, the most abundant collagen type in bone, are also detailed, including its triple-helix structure and the role of posttranslational modifications in maintaining its stability and function. The review underscores the critical role of collagen in bone's mechanical properties, particularly its toughness, and the impact of collagen alterations on bone strength.This review by S. Viguet-Carrin, P. Garnero, and P.D. Delmas explores the role of collagen in bone strength. Bone strength is influenced by both the quantity and quality of bone tissue, with the latter characterized by geometry, microarchitecture, turnover, mineral content, and collagen. The review highlights the interplay between type I collagen and minerals, emphasizing the importance of collagen fiber orientation under mechanical forces. It discusses various maturation processes of collagen, including enzymatic and nonenzymatic modifications, such as the formation of crosslinks by lysyl oxidase and the accumulation of advanced glycation end products. These modifications can affect bone strength and are associated with conditions like osteogenesis imperfecta and osteoporosis. The synthesis and structure of type I collagen, the most abundant collagen type in bone, are also detailed, including its triple-helix structure and the role of posttranslational modifications in maintaining its stability and function. The review underscores the critical role of collagen in bone's mechanical properties, particularly its toughness, and the impact of collagen alterations on bone strength.