Objectives Design and build a portable xenon-129 (¹²⁹Xe) hyperpolariser for clinically accessible ¹²⁹Xe lung MRI. Methods The polariser system consists of six main functional components: (i) a laser diode array and optics; (ii) a B₀ coil assembly; (iii) an oven containing an optical cell; (iv) NMR and optical spectrometers; (v) a gas-handling manifold; and (vi) a cryostat within a permanent magnet. All components run without external utilities such as compressed air or three-phase electricity, and require just three mains sockets for operation. The system can be manually transported in a lightweight van and rapidly installed on a small estates footprint in a hospital setting. Results The polariser routinely provides polarised ¹²⁹Xe for routine clinical lung MRI. To test the concept of portability and rapid deployment, it was transported 200 km, installed at a hospital with no previous experience with the technology and ¹²⁹Xe MR images of a diagnostic quality were acquired the day after system transport and installation. Conclusion This portable ¹²⁹Xe hyperpolariser system could form the basis of a cost-effective platform for wider clinical dissemination and multicentre evaluation of ¹²⁹Xe lung MR imaging. Advances in knowledge Our work successfully demonstrates the feasibility of multicentre clinical ¹²⁹Xe MRI with a portable hyperpolariser system.