Two sublime individual goals from Roberto Pereyra and Gerard Deulofeu helped Watford secure their best ever start to a top-flight season and send Huddersfield to the foot of the table.
The visitors began brightly at Vicarage Road, Aaron Mooy testing Ben Foster with a rasping drive from the edge of the area before Alex Pritchard sent a curling effort narrowly over the crossbar.
But David Wagner's side fell behind when Pereyra slotted home following a mazy run into the Terriers' box, before Deulofeu thumped past Jonas Lossl from a tight angle to double the hosts' lead.
Foster was forced to tip Chris Lowe's long-range drive on to the crossbar soon afterwards, but Isaac Success added a third for Watford in the second half to secure a comfortable victory for Javi Gracia's men.