<p>Terahertz (THz) metalenses have attracted considerable attention as compact and efficient alternatives to conventional bulky optics. In particular, all-silicon metalenses leveraging the high refractive index of silicon (n ≈ 3.4) have been extensively studied in the THz regime. However, a systematic quantitative comparison of such metalenses with commercial THz optics has been lacking. Here, the design and experimental demonstration of monolithic all-silicon THz metalenses, fabricated on high-resistivity silicon (&gt; 10,000 Ω∙cm) using standard photolithography and deep reactive ion etching, are reported. Optimized cylindrical meta-atoms provided nearly 2π phase control and &gt; 90% transmission compared to the bare Si substrate, as confirmed by THz time-domain spectroscopy (THz-TDS) measurements. Inch-scale metalenses were fabricated and systematically compared with a commercial TPX refractive lens. The commercial lens exhibited negligible dispersion over a broad range of 0.3–1.3 THz, yet its focusing performance was limited by a focal spot size that deviated increasingly from the diffraction limit at higher frequencies. In contrast, the all-silicon metalenses operated effectively in the 0.9–1.2 THz range due to their inherent dispersion. They achieved ~ 24% smaller focal spot sizes at 1 THz and progressively approached the diffraction limit at higher frequencies, highlighting their superior focusing performance. Furthermore, a vortex beam plate generating an orbital angular momentum (OAM) mode with ℓ = 1 was realized, demonstrating the multifunctional capability of the platform. Our results underscore the potential of monolithic all-silicon metasurfaces as compact and efficient optical elements for THz applications.</p>