Quantum emitters in hexagonal boron nitride (hBN) are promising building blocks for the realization of integrated quantum photonic systems. However, their spectral inhomogeneity currently limits their potential applications. Here, we apply tensile strain to quantum emitters embedded in few-layer hBN films and realize both red and blue spectral shifts with tuning magnitudes up to 65 meV, a record for any two-dimensional quantum source. We demonstrate reversible tuning of the emission and related photophysical properties. We also observe rotation of the optical dipole in response to strain, suggesting the presence of a second excited state. We derive a theoretical model to describe strain-based tuning in hBN, and the rotation of the optical dipole. Our work demonstrates the immense potential for strain tuning of quantum emitters in layered materials to enable their employment in scalable quantum photonic networks.Single photon emitters (SPEs) embedded in solid state hosts are critical building blocks for a range of quantum technologies. [1][2][3] Integrating SPEs with on-chip nanophotonic components provides a scalable route towards the engineering of quantum gates and quantum circuitry. [4][5][6] However, unwanted interactions between the atom-like defects and the crystal host environment lead to spectral inhomogeneity that hinders device performance. To address this issue, methods for tuning emitter properties are critical for generating identical photons, [7][8][9] and for coupling to high-quality factor photonic resonators, where tuning magnitudes must be comparable to or greater than the cavity linewidths. [10] Recently, hexagonal boron nitride (hBN), has been shown to host a range of sub-band gap defects operating as room temperature SPEs. [11][12][13][14] These SPEs display a number of desirable properties, including high photon purity, [15] bright emission, [16] and favorable quantum efficiencies. [17] However, the emitters have been shown to be susceptible to environmental influences, which lead to extreme inhomogeneity in their emission properties, [18] including a broad, continuous spectral range of zero phonon lines spanning from the deep ultraviolet to the near infrared. [19][20][21] Consequently, reliable tuning methods for controlling the emission properties are paramount for their implementation in quantum photonic applications.