Applications are invited for a Postdoctoral Researcher in Observational and Theoretical Cosmology. The successful candidate will work together with Prof. David Alonso and others at the Beecroft Institute of Particle Astrophysics and Cosmology (BIPAC), on research aimed at extracting cosmological information from large-scale structure (LSS) and Cosmic Microwave Background (CMB) probes on very large scales. This work will exploit data from the Rubin Observatory and the Simons Observatory, as well as publicly-available datasets. In addition to David Alonso’s research group, you will work within the broader cosmology group at Oxford, who combine expertise on a wide variety of topics in theoretical, observational, and numerical cosmology and astrophysics. The successful candidate will be required to develop a personal research programme in observational or theoretical cosmology, with a particular emphasis on ultra-large-scale cosmology (including primordial non-Gaussianity and horizon-sized effects). The candidate will be required to demonstrate the ability to manage their own academic research and administrative activities which may involve small scale project management, to co-ordinate multiple aspects of work to meet deadlines. The candidate will take part in the academic life of BIPAC and the astrophysics group at the Physics Department, and in particular attending and taking part in seminars, colloquia and journal clubs and will have the opportunity to teach. Applicants should have a PhD (or close to completion) in Physics, Astrophysics or a related field. Previous experience in the field of Cosmology, Computational Astrophysics, Early Universe or Gravitational Physics will be an advantage as well as experience in the analysis or modelling of LSS data, including (but not limited to) galaxy clustering and CMB lensing. Please direct inquiries to Prof. David Alonso (david.alonso@physics.ox.ac.uk). The post is full time and fixed term for two years with a possibility of further extension. The closing date for applications is noon GMT, 5 January 2026 As part of the online application, you will be asked to upload a CV (including a publications list), a three-page research statement (not including references), and details of two referees as part of your online application. Your referees should be asked to send their letters, before the application deadline, to Leanne O’Donnell ( leanne.odonnell@physics.ox.ac.uk ) by the closing date.