Haa Dhaalu Atoll is the code name based on the letters of the Maldivian alphabet commonly used to refer to the administrative division (known as "Atoll") officially known as South Thiladhunmathi Atoll (Maldivian: Thiladhunmathi Dhekunuburi) in the Maldives.
The administrative division consists of the southern section of natural Thiladhunmathi Atoll (which is shared with North Thiladhunmathi (Haa Alifu) Atoll) and Makunudhoo or Maamakunudhoo Atoll (Malcolm Atoll in the Admiralty Charts) with its large reef.