Sidoarjo Regency (Javanese: ꦑꦧꦸꦥꦠꦺꦤ꧀ꦱꦶꦢꦲꦂꦗ, romanized: Kabupatèn Sidaharja) is a regency in East Java, Indonesia. It is bordered by Surabaya City and Gresik Regency to the north, by Pasuruan Regency to the south, by Mojokerto Regency to the west, and by the Madura Strait to the east. It has a land area of 719.34 km, making it the smallest regency in East Java, although it contains many of the southern suburbs of Surabaya and has a high population density.

As at the 2010 census, Sidoarjo Regency had a population of 2,191,489 while the 2020 census showed a small decline to 2,033,760, notably in the northern part of the regency immediately bordering Surabaya; the official estimate as at mid-2023 showed a further decline to 1,996,825 (comprising 1,000,067 males and 996,758 females). The regency is part of the urban region surrounding Surabaya, known as the 'Gerbangkertosusila' area.

The Sidoarjo Regency is divided into eighteen administrative districts (kecamatan). The districts are tabulated below with their areas and their populations at the 2010 census and the 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 in each district (totaling 322 rural desa and 31 urban kelurahan), and its post code.

Kode Wilayah	Name of District (kecamatan)	Area in km	Pop'n census 2010	Pop'n census 2020	Pop'n estimate mid 2023	Admin centre	No. of villages	Post code
35.15.01	Tarik	36.06	61,032	69,189	67,458	Mergosari	20	61265
35.15.02	Prambon	34.22	68,576	79,952	78,460	Prambon	20	61264
35.15.03	Krembung	29.55	58,336	69,887	68,402	Mojoruntul	19	61275
35.15.04	Porong	29.82	64,390	73,446	70,170	Juwetkenongo	19	61274
35.15.05	Jabon	81.00	49,567	56,266	55,153	Dukuhsari	15	61276
35.15.06	Tanggulangin	32.29	83,304	89,804	87,161	Kalitengah	19	61272
35.15.07	Candi	40.67	145,155	153,423	153,922	Gelam	24	61271
35.15.09	Tulangan	31.21	84,582	102,339	101,177	Kenongo	22	61273
35.15.10	Wonoayu	33.92	71,822	85,586	83,764	Wonoayu	23	61261
35.15.14	Sukodono	32.68	110,596	121,859	121,954	Anggaswangi	19	61216 - 61258
35.15.08	Sidoarjo	62.56	193,469	201,120	197,756	Sidokumpul	24	61212 - 61234
35.15.15	Buduran	41.03	91,931	98,710	98,999	Banjarkemantren	15	61252
35.15.17	Sedati	79.43	92,786	96,636	95,277	Pulungan	16	61253
35.15.18	Waru	30.32	231,309	200,754	194,084	Janti	17	61256
35.15.16	Gedangan	24.06	132,971	120,003	118,338	Keboansikep	15	61254
35.15.13	Taman	31.54	213,224	207,815	200,405	Bebekan	24	61212 - 61257
35.15.11	Krian	32.50	131,281	130,930	130,412	Kraton	22	61262
35.15.12	Balongbendo	31.40	66,841	76,050	73,933	Wonokupang	20	61263
	Totals	714.24	2,191,489	2,033,764	1,996,825	Sidoarjo	353

Notes: (a) comprising 6 kelurahan (Gedang, Jatirejo, Juwetkenongo, Mindi, Porong and Siring) and 13 desa.
(b) comprising 14 kelurahan (Bulusidokare, Celep, Cemengkalang, Gebang, Lemahputro, Magersari, Pekauman, Pucang,
Pucanganom, Sekardangan, Sidokare, Sidoklumpuk, Sidokumpul and Urangagung) and 8 desa.
(c) comprising 8 kelurahan (Bebekan, Geluran, Kalijaten, Ketegan, Ngelom, Sepanjang, Taman and Wonocolo) and 16 desa.
(d) including 3 kelurahan (Kemasan, Krian and Tambak Kemerakan).

As a satellite region and part of Greater Surabaya, the Sidoarjo economy is valued at 197.24 Trillion IDR in 2020 and is the second-largest in East Java after Surabaya.

Primary Sector

Although Sidoarjo Regency's land area is relatively small and densely populated, the primary sector still maintains a role in Sidoarjo's economy. Agriculture is mainly produced in the western and southwestern parts of Sidoarjo Tulangan District, Krembung District, and Balongbendo District. During the colonial era, Sidoarjo was famous for sugarcane production and it hosted several sugar mills owned by the Colonial government. After Independence, the Indonesian government nationalised all sugar mills in Sidoarjo. The sugarcane production sector peaked in the 70s and gradually declined since then, due to inflows of manufacturing investment and rapid urbanization that reduced the sugarcane planting area. Today, crops that still produced in Sidoarjo are Rice, Banana, Papaya, Cassava, and several lowland vegetables.

Fisheries also still maintain a role. In the past, Sidoarjo was known as a fishing town, but the fishing sector was slowly declining as Sidoarjo became more urbanized. Today, fishing has been replaced by aquaculture as the main source of fish in Sidoarjo. Highly productive aquaculture is mainly produced in the eastern part of Sidoarjo Regency, and the main product is Milkfish and farmed shrimp which are mostly exported to the US and Japan. Sidoarjo is also famous for its processed fishery products, such as prawn cracker, fish cracker, shrimp paste and petis.

The mining sector could be neglected as it contributes very little to Sidoarjo economy. The main mining sector is natural gas, which is produced in Porong District. There are also several sand miners that operate in Jabon District.

Secondary Sector

Manufacturing is a main sector of the Sidoarjo economy with a contribution of nearly 40%. Sidoarjo manufacturing production is diversified and ranges from furniture to electronics products. There are numerous manufacturing plants in Sidoarjo. Among this are : Jatim Taman Steel (Steel Manufacturer), Avian (Paints and building material), Tunggal Djaja (Paints Production), Maspion (Household durable goods), Japfa Comfeed (Feedmills and poultry), Interbat (Pharmaceuticals), Integra (Furniture), Tjiwi Kimia (Paper), Kimberly-Clark's Softex (Non-durable consumer goods), Unicharm (Non-durable consumer goods), Polygon Bikes (Bikes), Alumindo (Aluminium products), Sekar Group (Food processing), Hisamitsu (Pharmaceutical), Lighting Solutions (Lamp), ECCO (Footwear), Samator (Industrial gas and chemicals), Bernofarm (Pharmaceutical), Muntjul Diamond (Vehicle body), Charoen Pokphand (Agribusiness) and many more.

There are thousands small and medium manufacturers established in Sidoarjo. Garments, Food Processing, Footwear, Apparel, and Furniture are products that usually produced by small and medium manufacturers in Sidoarjo. Many small and medium manufacturers produces Traditional Herbs, Machinery, Packaging, and Metal products.

During colonial era, there are ten sugarmills in Sidoarjo and the oldest is Watu Tulis Sugarmills that built in 1838. Today, there are remain three sugarmills that still operated in Sidoarjo. Among this are New Candi Sugarmills that built in 1911, Krembung Sugarmills, and Watu Tulis Sugarmills.

Tertiary Sector

The main tertiary sectors in Sidoarjo are wholesaling and retailing, food services, education, and financial services. As Sidoarjo is getting more urbanized, the tertiary sector is predicted to grow significantly. The fastest growth in the tertiary sector is recording in experience-related services, such as food services (notably restaurant, cafe) and movie theater. Education Services are also predicted to grow, as several private tutoring companies are opening a branch in Sidoarjo and private schools are gaining more students, due to increasingly population, income, and lack of capacity in state schools.

Since May 2006, more than 10,000 people in the Porong District have been displaced by the hot mud flowing from a natural gas well being drilled by Lapindo Brantas, an oil well company that is part of a conglomerate owned by Coordinating Minister for the People's Welfare Aburizal Bakrie. Gas and hot mud started spewing from the well on May 28, when the drill penetrated a layer of liquid sediment. Attempts to pump concrete down the well did not stop the flow. While some scientists have speculated that the earthquake that struck Yogyakarta on May 27, the day before the well erupted, may have cracked the ground, creating potential pathways for the mud to reach the surface, others have suggested that the drilling procedure was faulty by not using a casing. This is likely to be incorrect as technical papers on the subject showed that there were up to four sets of casing installed and cemented in the well. Some 50,000 cubic metres of hot mud were erupting every day as of August; in September, the amount increased to some 125,000 cubic metres daily. On September 26 barriers built to hold back the mud failed, resulting in the flooding of more villages. Gus Maksum, one of the thousands of Sidoarjo villagers displaced by the mud flow gives a detailed first-hand account of the first year of the disaster in his memoir Titanic Made By Lapindo. As of late September 2006 scientists are saying that the eruption may be a mud volcano forming, and may be impossible to stop.

Sidoarjo has a tropical monsoon climate (Am) with moderate to little rainfall from May to November and heavy rainfall from December to April.

{Culinary} Sidoarjo has lots of worth to culinary tastes, from sour and spicy, to sweet culinary. Sour food in Sidoarjo can be described as a fruity dish called Rujak, and the most famous ones are Lontong Kupang, Sate Kerang, and Lontong Balap which are very spicy. And Klepon is a sweet dessert wrapped by a coconut zest.