Khalfehlu (Persian: خلفلو) is a village in, and the capital of, Sanjabad-e Shomali Rural District of the Central District of Kowsar County, Ardabil province, Iran.

At the 2006 census, its population was 111 in 26 households. The following census in 2011 counted 83 people in 25 households. The latest census in 2016 showed a population of 42 people in 13 households.