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We present Herschel observations of 6 fine-structure lines in 25 ultraluminous infrared galaxies at z< 0.27. The lines,[O iii] 52 μm,[N iii] 57 μm,[O i] 63 μm,[N ii] 122 μm,[O i] 145 μm, and [C ii] 158 μm, are mostly single Gaussians with widths< 600 km s− 1 and luminosities of 10 7–10 9 L☉. There are deficits in the [O i] 63/L IR,[N ii]/L IR,[O i] 145/L IR, and [C ii]/L IR ratios compared to lower luminosity systems. The majority of the line deficits are consistent with dustier H ii regions, but part of the [C ii] deficit may arise from an additional mechanism, plausibly charged dust grains. This is consistent with some of the [C ii] originating from photodissociation regions or the interstellar medium (ISM). We derive relations between far-IR line luminosities and both the IR luminosity and star formation rate. We find that [N ii] and both [O i] lines are good tracers of the IR luminosity and star formation rate. In contrast,[C ii] is a poor tracer of …