Titanohematites are rhombohedral Fe–Ti oxides with variable compositions (Fe2–yTiyO3, 0 ≤ y ≤ 1) and solid solution between hematite (α-Fe2O3, y = 0) and ilmenite (FeTiO3, y = 1) end members. Like hematite, titanohematites with 0 ≤ y ≤ 0.45 have canted antiferromagnetic structures with spins parallel to the basal plane and weak but hard spontaneous magnetizations. Complex magnetic and cation ordering and subsolvus exsolution variations control titanohematite composition and magnetism. During slow magma cooling, a single homogeneous phase is thermodynamically unstable so that two phases close to the hematite and ilmenite end members form. Nanoscale contact layers between ilmenite–hematite lamellae have strong ferrimagnetism in contrast to canted antiferromagnetic hematite and antiferromagnetic ilmenite. Exsolution is inhibited during rapid cooling, and metastable intermediate phases form. Inhomogeneous cation diffusion produces fine-scale antiphase domains between adjacent Fe-rich and Ti-rich layers so that ferrimagnetic behaviour occurs for compositions with y > 0.45. Self-reversed magnetizations also occur due to coupling between magnetic and cation ordering in these titanohematites.