Abstract: High density brine compositions may be formulated including water and at least one rare earth nitrate salt, where the at least one rare earth salt is present in an amount effective for the high density brine composition to have a density in the range of about 8.5 to about 21 pounds per gallon (about 1020 to about 2500 kg/m3). Suitable rare earth nitrate salts include, but are not necessarily limited to, lanthanum nitrate (La(NO3)3), cerium nitrate (Ce(NO3)3), scandium nitrate, and/or yttrium nitrate. Alkaline earth metal salts such as, but not limited to, calcium bromide (CaBr2), and alkali metal salts and metal salts may also be used with the rare earth nitrate salt(s). In one non-limiting embodiment the high density brines have an absence of zinc and cesium salts. These high density brine compositions may be suitably used for completion fluids in hydrocarbon recovery operations.