Marine Isotope Stage 9 (MIS 9) is a Marine Isotope Stage in the geological record. It is the final period of the Lower Paleolithic, and lasts from 337,000 to 300,000 years ago according to Lisiecki and Raymo's LR04 Benthic Stack, which has been adopted by the Subcommission on Quaternary Stratigraphy of the International Commission on Stratigraphy. It was an interglacial (warm period) which corresponds to the Purfleet Interglacial in Britain, and falls within the Pre-Illinoian in North America. Some authorities regard it as corresponding to the Holstein Interglacial in continental Europe.
Europe was then occupied by Homo heidelbergensis, but they had probably retreated from Britain during the preceding glacial period. Populations returned as the climate warmed and sea levels rose around 330,000 years ago, and thousands of hand axes and other artefacts have been found along the terraces of the Thames and former Solent rivers. In Southern England, the summers were similar to or slightly warmer than today, and the winters slightly cooler. The period saw a transition from Clactonian to Clactonian culture for manufacture of stone tools.
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- "Version history of the Quaternary chronostratigraphical chart". The Subcommission on Quaternary Stratigraphy. 2011.
- Ashton, Nick (2017). Early Humans. London: William Collins. p. 155. ISBN 978-0-00-815035-8.
- Editorial (July 2016). "The Hoslteinian period in Europe (MIS 11-9)". Quaternary International. 409: 1. Bibcode:2016QuInt.409....1M. doi:10.1016/j.quaint.2016.06.006.
- Ashton, Nick (2017). Early Humans. London: William Collins. p. 155-59. ISBN 978-0-00-815035-8.
- McNabb, John (2011). The British Lower Palaeolithic: Stones in Contention. Routledge. p. 163. ISBN 9781134090556.