Platinum (Pt) is an emerging critical metal, but the long-term impact of Pt contamination remains largely unknown. The most common anthropogenic sources of Pt derive from use as a catalytic converter (deposited in road runoff) and as a cancer drug (excreted into sewage). We report, for the first time, Pt input from three major German rivers (Ems, Weser and Elbe) into the North Sea. Cruise M169 was conducted in December 2020 in the southern North Sea, from river endmembers (S = 0.4-0.5) to the more pristine Doggerbank region (S = 33-34). In addition, we followed a 12-h tidal cycle in each of the rivers. We found all three rivers to be a major source of Pt to the estuary, reaching a maximum of >6 pmol L^-1 in the Weser endmember, compared to < 1 pmol L^-1 near Doggerbank. In general, Pt concentrations followed a conservative distribution relative to salinity, although in the Elbe, an initial sharp drawdown at low salinity (S < 1.5) was observed, indicating particle adsorption and/or colloidal flocculation. All samples measured in the North Sea were elevated in Pt (&#8805; 0.5 pmol L^-1) relative to open-ocean values (~0.2 pmol L^-1). Further research is needed (e.g., size fractionation and particle analysis) to evaluate the sources of Pt (anthropogenic vs. naturally occurring) into north German rivers and North Sea.