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We present six epochs of spectropolarimetric observations and one epoch ofspectroscopy of the Type Ib SN iPTF 13bvn. The epochs of these observationscorrespond to $-$10 to $+$61 days with respect to the {\it r}-band light curvemaximum. The continuum is intrinsically polarised to the $0.2-0.4\%$ levelthroughout the observations, implying asphericities of $\sim10\%$ in the shapeof the photosphere. We observe significant line polarisation associated withthe spectral features of Ca II IR3, He I/Na I D, He I {\lambda}{\lambda}6678,7065, Fe II {\lambda}4924 and O I {\lambda}7774. We propose that an absorptionfeature at $\sim 6200\mathrm{\AA}$, usually identified as Si II $\lambda 6355$,is most likely to be high velocity $\mathrm{H\alpha}$ at $-16,400$ $\mathrm{km\; s^{-1}}$. Two distinctly polarised components, separated in velocity, aredetected for both He I/Na I D and Ca II IR3, indicating the presence of twodiscrete line forming regions in the ejecta in both radial velocity space andin the plane of the sky. We use the polarisation of He I $\lambda 5876$ as atracer of sources of non-thermal excitation in the ejecta; finding that thebulk of the radioactive nickel was constrained to lie interior to $\sim50-65\%$ of the ejecta radius. The observed polarisation is also discussed inthe context of the possible progenitor system of iPTF 13bvn, with ourobservations favouring the explosion of a star with an extended, distortedenvelope rather than a compact Wolf-Rayet star.

Spectropolarimetry of the Type Ib Supernova iPTF 13bvn: Revealing the complex explosion geometry of a stripped-envelope core-collapse supernova