We present an extensive set of photometric and spectroscopic data for SN 2009jf, a nearby Type Ib supernova (SN), spanning from ~20d before B-band maximum to 1yr after maximum. We show that SN 2009jf is a slowly evolving and energetic stripped-envelope SN and is likely from a massive progenitor (25-30M_{sun}_). The large progenitor's mass allows us to explain the complete hydrogen plus helium stripping without invoking the presence of a binary companion.