We report the first chalcogenide-based optical parametric oscillator (OPO) relying on pure parametric gain. The all-fiber OPO operates in the wavelength range of 2 μm and is tunable over 290 nm from the combined Stokes and anti-Stokes contributions. The gain medium is a 10 cm long chalcogenide microwire made from a high modal confinement As2Se3 core with cyclo olefin polymer cladding, leading to optimized chromatic dispersion, high nonlinearity, and broadband transparency. With a power threshold of only a fraction of a milliwatt, this design is promising for the fabrication of tunable, compact, and low-power consumption mid-infrared sources.