Abstract
The first fully correlated calculations of the magnetic moment in lithium are presented. Relative to the free-electron value, the Zeeman gJ factor for the ground state lithium gJ/ge1 is calculated to a computational accuracy of 200 parts in 109, including relativistic and radiative corrections of orders α2, α2m/M, and α3. The isotope shifts in gJ are predicted precisely for various isotopes. The extensions to the first excited S state of lithium and the ground state of Be+ are made.