According to Official Guinness Records,
The fastest half marathon wearing lederhosen is 1 h 36 min 39 sec and was achieved by Timothy Charles O’Brien (Australia) at the Blackmores Half Marathon, Sydney, Australia, on 16 September 2018. Timothy ran the marathon in memory of a friend.
For a complete list of 2018 records, please visit 2018 Guinness Records in Australia.