It is shown that thebinuclear heliumlike atom(D+D+)2e−, where the D+−D+nuclear separation is of the order of 0.5a0(a0being the Bohr radius) and the electron configuration resembles that of the helium atom, is a metastable configuration which can be formed by overcoming an energy barrier of the order of 2E0(−E0being the hydrogen ground‐state electronic energy). Since the temperature conditions allowing the binuclear heliumlike atoms to be formed are obtained during the implantation of heavy clusters into deuterated targets, (D+D+)2e−seems the natural candidate to explain thewarm fusionevents observed during the impact of heavy water clusters onto titanium deuteride. The hypothesis that (D+D+)2e−is the fusing species in othercold fusionphenomena (electrolytic fusion, fusion induced by a thermodynamic instability, and chemofusion) is discussed.