A particularly intriguing subclass of rocky exoplanets are the ultra- short period (USP) worlds that orbit their host stars in less than a day. These planets are particularly rare around M dwarf stars, with so far only ten that have a constrained mass and radius. We present the validation and characterisation of the ultra-short period (0.3 days), Earth-sized planet TOI-4552 b orbiting a nearby (27.26pc away) M4.5V dwarf. Complementing the TESS photometry, ground-based transit observations from LCO, ExTrA and SPECULOOS validated the planetary radius and cleared the field of any contaminants. Speckle imaging with Zorro (Gemini-S) rules out false positive scenarios caused by eclipsing binary sources. Spectroscopic observations with NIRPS and HARPS were used to obtain stellar abundances, constrain the planetary mass, and, in conjunction with the transit observations, estimate the orbital parameters. TOI-4552 is a quiet star exhibiting no short-term stellar variations seen in photometric or radial velocity data that can be associated to stellar rotation. Long-term photometric data from ASAS-SN also suggests a lack of activity signals. TOI-4552 b (Mp=1.83+/-0.47M_{Earth}_, Rp=1.11+/-0.04R_{Earth}_) lies between the Earth-like and iron-rich composition tracks on the Mass-Radius diagram. The exopie interior structure model, without constraints from refractory abundance ratio, yields a core mass fraction (CMF) of 0.54^+0.17^_-0.25_ and a bulk density of 7.74g/cm^3^. Since the CMF spans a wide range due to the large uncertainty on the mass, the definitive interior composition cannot be determined with the current dataset. TOI-4552 b hints as being marginally more iron- rich compared to the Earth but confirmation of its status requires additional, precise radial velocity measurements. Combined with its high emission spectroscopic metric (ESM=19.5), negligible stellar activity and short orbital period, TOI-4552 b emerges as a compelling target for atmospheric and surface composition studies with JWST.