A total of 603 seawater samples were analysed for their lithium concentrations. The seawater samples were collected during eight research expeditions. All seawater lithium concentrations were normalised to TEOS-10 absolute salinity of 35 g/kg. Most seawater samples were collected using Niskin bottles and filtered using 0.22 µm filters. Exceptions are samples UW1-UW26 that were collected from the underway water system of RV Kilo Moana during cruise CDisK-IV, and surface water samples from the Red Sea that were collected using a bucket lowered from the deck of a container ship. Samples from cruises SOE09, RS2015 and RS2018 were not filtered. The seawater samples were collected during the following cruises: CDisK-IV from Hawaii to Alaska in 01-30 August 2017; SN105 from Goa to Mauritius, samples collected during 7-16 December 2015; RS2015 from the Bay of Bengal to the Mediterranean Sea, samples collected during 27 December 2015 to 3 January 2016; RS2018 from the Bay of Bengal to the Mediterranean Sea, samples collected during 23-31 March 2018; SOE09 in the Indian sector of the Southern Ocean in 12 January - 21 February 2017; JR274 in the Atlantic sector of the Southern Ocean between 9 January and 12 February 2013; D357 and JC068 sailed from South Africa to South America, mostly along 40°S, cruise D357 in 18 October – 22 November 2010, and cruise JC068 in 24 December 2011 – 27 January 2011.