Lifeworkers were the third-highest rate in Forerunner society. They specialized in all living things and medicine, including experimenting with new forms of life. The highest possible rank achievable by a Lifeworker was Lifeshaper.
The Lifeworkers, under the Librarian's control, were responsible for maintaining the ecosystems on Installation 00 and the Halo Array using them to research, store and index species collected from numerous worlds across the galaxy in the Conservation Measure. Earth, then called "Erde-Tyrene", was at one point an experimental planet under the care of the Librarian, a Lifeshaper and one of the most powerful Lifeworkers to have ever lived.
Lifeworker forms were typically graceful and tall compared to other rates. Lifeworkers appeared to prefer to float using parts of their armor, as opposed to walking like most Forerunners. This is seen quite prominently with the Librarian and her Lifeworkers on Omega Halo.
 Known Lifeworkers
- Genemender Folder of Fortune
Two Lifeworkers surveying the effects of the Composer on a human village on Omega Halo.
 List of appearances
- Halo: Cryptum (First appearance)
- Halo: Combat Evolved Anniversary
- Halo: Primordium
- Halo 4
- Halo: Silentium
- ^ Halo Waypoint: Halo: Cryptum Glossary
- ^ Halo: Cryptum, page 334
- ^ Halo: Cryptum, page 17
- ^ Halo: Cryptum, page 330