Purely organic ferromagnets are rare, the main problem being the relative orientation of the spins in a three-dimensional network. The first example of ferromagnetic ordering in an imino-nitroxide radical is reported. A detailed analysis of the structure reveals that CCH-O hydrogen bonds are responsible for both the crystal packing and the ferromagnetic spin interactions within an infinite chain of ordered molecules. This radical is unique: its structure is the first demonstration of the use of terminal acetylenes to generate supramolecular networks.