We present a full ΛCDM analysis of the BOSS DR12 dataset, including information from the power spectrum multipoles, the real-space power spectrum, the reconstructed power spectrum and the bispectrum monopole. This is the first analysis to feature a complete treatment of the galaxy bispectrum, including a consistent theoretical model and without large-scale cuts. Unlike previous works, the statistics are measured using window-free estimators: this greatly reduces computational costs by removing the need to window-convolve the theory model. Our pipeline is tested using a suite of high-resolution mocks and shown to be robust and precise, with systematic errors far below the statistical thresholds. Inclusion of the bispectrum yields consistent parameter constraints and shrinks the σ8 posterior by 13% to reach < 5% precision; less conservative analysis choices would reduce the error-bars further. Our constraints are broadly consistent with Planck : in particular, we find H0 = 69.6 +1.1 −1.3 km s −1 Mpc −1 , σ8 = 0.692 +0.035 −0.041 and ns = 0.870 +0.067 −0.064 , including a BBN prior on the baryon density. When ns is set by Planck, we find H0 = 68.31 +0.83 −0.86 km s −1 Mpc −1 and σ8 = 0.722 +0.032 −0.036 . Our S8 posterior, 0.751 ± 0.039, is consistent with weak lensing studies, but lower than Planck. Constraints on the higher-order bias parameters are significantly strengthened from the inclusion of the bispectrum, and we find no evidence for deviation from the dark matter halo bias relations. These results represent the most complete full-shape analysis of BOSS DR12 to-date, and the corresponding spectra will enable a variety of beyond-ΛCDM analyses, probing phenomena such as the neutrino mass and primordial non-Gaussianity.