These are the best Pentax prime lenses when you want compact metal builds, creamy rendering, and weather-ready confidence across APS-C and full-frame K-mount bodies—from street and travel to portraits, astro, and product work. The modern full-frame flagships are the HD PENTAX-D FA★ 50mm f/1.4 SDM AW and HD PENTAX-D FA★ 85mm f/1.4 SDM AW: fast, razor-sharp, beautifully corrected for fringing, and sealed for rain-soaked weddings or night streets, with smooth bokeh and decisive AF for hybrid shooters. Limited-series gems bring signature rendering in tiny, tactile barrels: the HD PENTAX-D FA 21mm f/2.4 Limited DC WR is a weather-sealed wide with modern coatings and story-rich micro-contrast; the FA Limited “Trinity”—31mm f/1.8, 43mm f/1.9, 77mm f/1.8—delivers classic glow, elegant sunstars, and skin-friendly tone that make them beloved for environmental portraits and editorial travel; add the HD PENTAX-DA 40mm f/2.8 Limited and HD PENTAX-DA 70mm f/2.4 Limited on APS-C for featherweight street and flattering tele looks in pocketable form. Macro and detail specialists should grab the HD PENTAX-D FA 100mm f/2.8 Macro WR for 1:1 sharpness, rounded blades, and WR metal build, or the HD PENTAX-DA 35mm f/2.8 Macro Limited on APS-C for true 1:1 in a walk-around FOV with jewel-like construction; budget shooters can lean on the DA 35mm f/2.4 and DA 50mm f/1.8 for light, sharp, no-drama primes that pair beautifully with in-body SR. Low-light and portrait fans on APS-C get the smc/HD PENTAX-DA★ 55mm f/1.4 SDM for creamy separation and weather-resistant confidence, while full-frame users can mix in characterful classics like the smc/HD PENTAX-FA 50mm f/1.4 for vintage glow or the FA 35mm f/2 for a crisp, compact wide-normal. Ultra-wide prime options expand creative horizons: the IRIX 15mm f/2.4 (K-mount) offers long-throw manual focus, low coma for astro, and robust sealing; the Laowa 12mm f/2.8 Zero-D (K) brings rectilinear discipline for interiors and stars; and the Samyang 14mm f/2.8 (K) remains a budget staple for dramatic vistas. For tele compression with painterly bokeh, the Samyang 135mm f/2 ED (K) is a cult classic—sharp wide open with a smooth manual throw perfect for portraits and nightscapes. Across the lineup, Pentax body advantages amplify these primes: in-body Shake Reduction steadies dusk frames, Pixel Shift unlocks micro-detail on static scenes, Astrotracer turns fast wides into pinpoint star tools, and Quick-Shift MF on many Pentax lenses lets you fine-tune focus instantly after AF locks. Practical picks: choose D FA★ 50/1.4 and 85/1.4 for flagship full-frame portrait and low-light work; run D FA 21/2.4 Limited for compact, sealed wide; carry the FA 31/43/77 Limited set when you want character in a tiny kit; grab DA 35/2.8 Macro Limited or D FA 100/2.8 WR for 1:1 detail; add DA 40 Limited or DA 70 Limited for pocket primes on APS-C; and look to IRIX 15/2.4, Laowa 12/2.8, or Samyang 135/2 for specialty wide or tele artistry. Whether you’re chasing neon on rainy streets, printing big landscape panoramas, styling products at 1:1, or crafting head-and-shoulders with velvet falloff, the best Pentax prime lenses combine Limited-series craftsmanship, modern star-grade optics, and Pentax’s in-body tech—so your images stay sharp, rich, and distinctly Pentax.