Paul Francis McMillan (3 June 1956 – 2 February 2022) was a British chemist who held the Sir William Ramsay Chair of Chemistry at University College London.

McMillan was born in Edinburgh, Midlothian, and brought up in Loanhead, a small mining and farming village at the base of the Pentland Hills.

[5] In 2000, McMillan returned to the United Kingdom, where he was made Professor of Solid State Chemistry at University College London, an appointment jointly held with the Royal Institution.

[6] New compounds and materials are prepared and studied at up to a million atmospheres and thousands of degrees Celsius using spectroscopy and synchrotron X-ray diffraction.

[6] McMillan has contributed across numerous fields and has published work relating to solid state inorganic/materials chemistry, high pressure-high temperature research,[8] amorphous solids and liquids,[9] vibrational spectroscopy,[10] synchrotron X-ray and neutron scattering, mineral physics, graphitic carbonitrides,[11] battery materials and the response of bacteria to high pressures.