That was estimated at ~200,000 km/h (~125,000 mph). Helios went 252,792 km/h (157,078) mph in the 1970s. - https://en.wikipedia.org/wiki/Helios_(spacecraft) ht

That was estimated at ~200,000 km/h (~125,000 mph). Helios went 252,792 km/h (157,078) mph in the 1970s. - https://en.wikipedia.org/wiki/Helios_(spacecraft) https://en.wikipedia.org/wiki/Helios_(spacecraft) The Parker Space Probe reached 466,592 km/h (289,927 mph) in 2020 - https://www.guinnessworldrecords.com/world-records/66135-fastest-spacecraft-speed https://www.guinnessworldrecords.com/world-records/66135-fas... . The plan is that Parker will reach 690,000 km/h (430,000 mph) by 2025. So "fastest" must be qualified with something like "achieved by direct human-designed acceleration".