Nature Cell Biology, Published online: 10 June 2026; doi:10.1038/s41556-026-01974-0 Oshio, Shiiba and colleagues show that HMOX2, which catalyses haem degradation, supplies haem-derived iron to mitochondria at ER–mitochondria contact sites in a process mediated by the mitochondrial ubiquitin ligase MITOL, also known as MARCH5/MARCHF5.