We present the smallest reported side-viewing needle probe for optical coherence tomography (OCT). Design, fabrication, optical characterization, and initial application of a 30-gauge (outer diameter $0.31\mathrm{mm}$ ) needle probe are demonstrated. Extreme miniaturization is achieved by using a simple all-fiber probe design incorporating an angle-polished and reflection-coated fiber-tip beam deflector. When inserted into biological tissue, aqueous interstitial fluids reduce the probe’s inherent astigmatism ratio to 1.8, resulting in a working distance of $300\mathrm{\mu m}$ and a depth-of-field of $550\mathrm{\mu m}$ with beam diameters below $30\mathrm{\mu m}$ . The needle probe was interfaced with an $840\mathrm{nm}$ spectral-domain OCT system and the measured sensitivity was shown to be only $7\mathrm{dB}$ lower than that of a comparable galvo-scanning sample arm configuration. 3D OCT images of lamb lungs were acquired over a depth range of $\sim 600\mathrm{\mu m}$ , showing individual alveoli and bronchioles.