In this study, single-crystal Si₃N₄:Eu²⁺ nanowires are successfully synthesized via a direct current arc plasma nitridation method. The as-synthesized product, characterized by X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy, consists of tightly packed bundles of nanowires. These nanowires have diameters ranging from tens to hundreds of nanometers and lengths up to several tens of micrometers. Under ultraviolet excitation, the nanowires display a bright yellow emission band centered at approximately 589 nm, which is attributed to the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ions. The photoluminescence properties are investigated under hydrostatic pressure up to 30 GPa. As the pressure increases, the Eu²⁺ emission band shows a significant and monotonic red shift at a rate of approximately 1.45 nm/GPa. This shift is primarily due to pressure-induced modifications in the energy level structure, resulting from reduced interionic distances and enhanced ionic interactions. Concurrently, the full width at half maximum (FWHM) of the emission band broadens with a pressure coefficient of about 0.8% GPa^–1, which can be explained by the combined effects of an enhanced crystal field, intensified electron-phonon coupling, lattice strain, and distortion. A pressure-sensing model based on chromaticity coordinate analysis is established, which demonstrates high performance with a maximum sensitivity of 0.78% GPa^–1. The stable correlation between these optical parameters and applied pressure enables high-precision sensing. The developed optical sensor exhibits a series of advantageous characteristics, including high sensitivity, a broad pressure detection range (up to 30 GPa), and excellent signal stability (maintaining 38% of the initial intensity at 23 GPa). These results indicate significant application potential for Si₃N₄:Eu²⁺ nanowires in high-pressure sensing under extreme conditions, such as deep-sea exploration, studies of planetary interiors, and monitoring of ultra-heavy construction.