Sitaro Islands Regency (Indonesian: Kabupaten Kepulauan Sitaro, although its formal name is Kabupaten Kepulauan Siau Tagulandang Biaro) is a regency located off the northern extremity of Sulawesi Island in the southern Sangihe Islands, North Sulawesi Province, Indonesia. The regency was formed under Law Number 15 Year 2007 from 2 January 2007 (Indonesian: Undang-Undang Nomor 15 Tahun 2007), by separation from the Sangihe Islands Regency of which it had previously formed the southern part. The short form of the name is formed from one syllable from each of the names of the three principal islands — Siau, Tagulandang and Biaro.

The main island is Siau, while further south (nearer Sulawesi) are Tagulandang and Biaro. The regency's area is 275.95 km and the total population was 63,801 at the 2010 census and 71,817 at the 2020 census; the official estimate as at mid 2023 was 72,883. Most of the population are fishermen and farmers. The religion of the majority of the population is Christianity and Catholicism, but there are also followers of Islam and Buddhism. The main town and administrative centre is Ulu Siau.

The regency is divided into ten districts (kecamatan), tabulated below with their areas and their populations at the 2010 census and 2020 census, together with the official estimates as at mid 2023. The table also includes the locations of the district administrative centres, the number of administrative villages (totaling 83 rural desa and 10 urban kelurahan) in each district, and its postal codes.

Kode Wilayah	Name of District (kecamatan)	Area in km	Pop'n census 2010	Pop'n census 2020	Pop'n estimate mid 2022	Admin centre	No. of villages	Post codes
71.09.07	Biaro	20.85	3,248	3,717	3,790	Lamanggo	5	95864
71.09.10	Tagulandang Selatan (South Tagulandang)	21.63	4,171	4,875	5,001	Kisihang	6	95866
71.09.03	Tagulandang (West Tagulandang)	55.53	11,597	13,215	13,457	Buhias	15	95863
71.09.06	Tagulandang Utara (North Tagulandang)	17.92	4,027	4,206	4,176	Bawoleu	6	95865
71.09.05	Siau Barat Selatan (Southwest Siau)	15.10	4,073	4,584	4,651	Talawid	7	95868
71.09.04	Siau Timur Selatan (Southeast Siau)	24.06	7,283	8,533	8,760	Sawang	14	95867
71.09.02	Siau Barat (West Siau)	34.92	7,849	8,799	8,918	Ondong	12	95862
71.09.09	Siau Tengah (Central Siau)	11.80	1,850	2,040	2,058	Beong	4	95860
71.09.01	Siau Timur (East Siau)	55.94	15,816	17,610	17,811	Ulu Siau	16	95861
71.09.08	Siau Barat Utara (Northwest Siau)	15.20	3,887	4,238	4,261	Hiung	8	95869
	Totals	275.95	63,801	71,817	72,883	Ulu Siau	94

Notes: (a) including 20 small offshore islands. (b) including the offshore islands of Pulau Ruang (the fourth largest island in the regency, with an active volcano at its centre), Pulau Pasige and 2 smaller.
(c) includes 2 kelurahan - Bahoi and Balehumara. (d) includes the small offshore island of Pulau Batuguhita.
(e) includes the offshore islands of Pulau Makaleki and the small Pulau Batuhasaho. (f) includes 3 kelurahan - Ondong, Paniki and Paseng.
(g) including the offshore islands of Pulau Pahepa, Pulau Gunatin, Pulau Mahoro and 13 smaller.
(h) includes 5 kelurahan - Akesimbeka, Bahu, Bebali, Tarorane and Tatahadeng. (i) includes the offshore islands of Pulau Batupuki Sewenahe and Pulau Timuhe.

Ondong, the seat of the regency has a tropical rainforest climate (Af) with heavy to very heavy rainfall year-round.