Haildhar Union () is a union, the smallest administrative body of Bangladesh, located in Anwara Upazila, Chittagong District, Bangladesh. The total population is 25,315.
The area of Haildhar Union is 3,885 acres (15.72 square kilometers).
According to the 2011 Bangladeshi census, Haildhar Union had a population of 25,315, of which 11,869 were males and 13,446 were females. The total number of households was 4,979.
Haildhar Union is located in the eastern part of Anwara Upazila, approximately 8 kilometres from the upazila headquarters. It is bordered on the west by Barakhain Union, Anwara Union, and Chatari Union; on the north by Barakhain Union and Paraikora Union; on the east by Paraikora Union, Barkal Union, Barama Union, Sangu River, and Chatari Union of Satkania Upazila; and on the south by Pukuria Union of Banshkhali Upazila.
Haildhar Union is the 10th Union Parishad under Anwara Upazila. The administrative activities of this union fall under the jurisdiction of Anwara Thana. It is part of Chittagong-13 (Constituency 290) of the National Parliament of Bangladesh. The villages of Haildhar Union are:
According to the 2011 Bangladeshi census, Haildhar Union had a literacy rate of 73.7%.
The Sangu River flows along the eastern and western sides of Haildhar Union. Additionally, the Chanikhali Canal, Iskhali-Kodala Canal, and Yunus Canal flow through this union.
The main markets in Haildhar Union are Malghar Bazar, Fakir Hat, Paler Hat, and Khodar Hat.