Decalithium is a highly rare isotope and element which is a necessary component in making red matter.
Traces of decalithium can still be found in the Hobus System, where it was used, along with protomatter, to trigger the Hobus supernova in 2387. "Catalyzed decalithium" can also cause shape-shifted Undine to revert to their natural forms upon exposure. Refined decalithium, on the other hand, can be used to prepare ship engines for travel through certain dense stellar nebulae, e.g, the Paulson Nebula.
- Decalithium was first mentioned in the Star Trek (2009) tie-in comic Countdown, Number One and again referenced in the Star Trek Online tie-in novel The Needs of the Many.