According to Official Guinness Records,
The longest marble run measures 2,858.9 m (9,379 ft 7 in) and was achieved by Sensirion AG-The Sensor Company (Switzerland) in Flumserberg, Switzerland, on 1 September 2017.Each year, Sensirion organises a team building event for their employees. This year they decided to attempt a Guinness World Records record attempt.
For a complete list of 2017 records, please visit 2017 Guinness Records in Switzerland.