A functorial and categorical defined cyclotomic trace is given, extending the usual one for rings to ring spectra. There are two ingredients to this: first a cyclotomic trace is needed that accepts a categorical input with few restrictive assumptions. This is important in its own right, since this allows one to transport rich structures through the cyclotomic trace. Secondly, a sufficiently nice model is needed for the category of finitely generated free modules which is functorial in the ring spectrum.where RM = M (1 + ) is the 'underlying' space of the Γ-space M , and where ΣX = Σ ∞ (X + ) is the 'suspension spectrum' of the unpointed space X which is given by taking Y ∈ ob Γ o to (ΣX)(Y ) = Y ∧ X + (Σ is strong monoidal, but R is only lax monoidal since the maps RM × RN −→ RM ∧ RN ∼ = R(M ∧ N ) and * −→ 1 + = R(S) are not isomorphisms). R S-categories. the cyclotomic trace for S-algebras % % J J J J J J J J J B(C, w) o o (C, w)