We investigate the regularity of cluster pressure profiles with REXCESS, a representative sample of 33 local (z < 0.2) clusters drawn from the REFLEX catalogue and observed with XMM-Newton. The sample spans a mass range of 10^{14^{< M_{500_{< 10^{15^{, where M_{500_{is the mass corresponding to a density contrast of 500. We derive an average profile from observations scaled by mass and redshift according to the standard self-similar model, and find that the dispersion about the mean is remarkably low, at less than 30 per cent beyond 0.2 R_{500_{, but increases towards the center. Deviations about the mean are related to both the mass and the thermo-dynamical state of the cluster. Morphologically disturbed systems have systematically shallower profiles while cooling core systems are more concentrated. The scaled profiles exhibit a residual mass dependence with a slope of ~0.12, consistent with that expected from the empirically-derived slope of the M_{500_{– Y_{X_{relation; however, the departure from standard scaling decreases with radius and is consistent with zero at R_{500_{. The scatter in the core and departure from self-similar mass scaling is smaller compared to that of the entropy profiles, showing that the pressure is the quantity least affected by dynamical history and non-gravitational physics. Comparison with scaled data from several state of the art numerical simulations shows good agreement outside the core. Combining the observational data in the radial range [0.03–1] R_{500_{with simulation data in the radial range [1–4] R_{500_{, we derive a robust measure of the universal pressure profile, that, in an analytical form, defines the physical pressure profile of clusters as a function of mass and redshift up to the cluster “boundary”. Using this profile and direct spherical integration of the observed pressure profiles, we estimate the integrated Compton parameter Y and investigate its scaling with M_{500_{and L_{X_{, the soft band X-ray luminosity. We consider both the spherically integrated quantity, Y_{sph_{(R), proportional to the gas thermal energy, and the cylindrically integrated quantity, Y_{cyl_{(R)=Y_{SZ_{D_{A_{^{2^{, which is directly related to the Sunyaev-Zel'dovich (SZ) effect signal. From the low scatter of the observed Y_{sph_{(R_{500_{) – Y_{X_{relation we show that variations in pressure profile shape do not introduce extra scatter into the Y_{sph_{(R_{500_{) – M_{500_{relation as compared to that from the Y_{X_{– M_{500_{relation. The Y_{sph_{(R_{500_{) – M_{500_{and Y_{sph_{(R_{500_{) – L_{X_{relations derived from the data are in excellent agreement with those expected from the universal profile. This profile is used to derive the expected Y_{SZ_{– M_{500_{and Y_{SZ_{– L_{X_{relations for any aperture.}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}

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