According to Official Guinness Records,
The largest Haka was achieved by 4,028 participants at an event organised by Mazda France and C.A. Brive Corrèze Limousin (both France) at the Stade Amédée Domenech in Brive-la-Gaillarde, France, on 27 September 2014.
For a complete list of 2014 records, please visit 2014 Guinness Records in France.