Cilacap Regency (Javanese: ꦏꦨꦸꦥꦠꦺꦤ꧀ꦕꦶꦭꦕꦥ꧀, also spelt: Chilachap, old spelling: Tjilatjap, Sundanese: ᮊᮘᮥᮕᮒᮦᮔ᮪ ᮎᮤᮜᮎᮕ᮪) is a regency (Indonesian: kabupaten) in the southwestern part of Central Java province in Indonesia. Its capital is the town of Cilacap.

Cilacap Regency covers an area of 2,249.28 km (including the 115-km Nusakambangan Island off the south coast), and it had a population of 1,642,107 at the 2010 Census and 1,944,857 at the 2020 Census; the official estimate as at mid-2023 was 2,007,829 (comprising 1,011,586 males and 996,243 females). The languages used in Cilacap are Javanese and Sundanese, but most people can speak Indonesian. The dialect used is Banyumasan.

There are schools of all levels in Cilacap and several higher-learning institutions. Several academies exist, such as Akademi Maritim Nusantara (National Maritime Academy). A polytechnic, Politeknik Cilacap, was established in 2008 and offers Engineering, Electronics and Informatics education.

Cilacap Regency comprises twenty-four districts (kecamatan), 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 (comprising 269 rural desa and 15 urban kelurahan - the latter all in the 3 Cilacap town districts), and its postcode. The three districts comprising Cilacap town formerly formed an Autonomous city but have now been subsumed back into the regency.

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
33.01.16	Dayeuhluhur	191.63	46,470	49,095	49,618	Dayeuhluhur	14	53266
33.01.15	Wanareja	195.92	92,824	105,580	107,479	Wanareja	16	53265
33.01.14	Majenang	167.60	122,763	140,329	143,101	Jenang	17	53257
33.01.13	Cimanggu	163.35	89,301	102,001	104,785	Cimanggu	15	53256
33.01.12	Karangpucung	124.74	68,412	79,096	80,927	Karangpucung	14	53255
33.01.18	Cipari	107.53	53,717	66,084	68,843	Cipari	11	53262
33.01.11	Sidareja	49.31	52,270	61,940	63,829	Sidareja	10	53261
33.01.01	Kedungreja	82.03	71,796	87,935	91,489	Ciklapa	11	53263
33.01.19	Patimuan	78.68	42,716	49,484	50,658	Patimuan	7	53264
33.01.10	Gandrungmangu	119.26	88,562	108,851	113,366	Gandrungmangu	14	53254
33.01.20	Bantarsari	99.49	60,795	74,555	77,597	Bantarsari	8	53281
33.01.09	Kawunganten	138.09	69,799	84,354	87,423	Kawunganten	12	53251
33.01.24	Kampung Laut	134.67	12,666	15,523	16,153	Klaces	4	53253
33.01.08	Jeruklegi	99.41	59,152	76,658	81,075	Jeruklegi Wetan	13	53252
33.01.02	Kesugihan	89.10	107,385	133,261	139,176	Kesugihan Kidul	16	53274
33.01.03	Adipala	74.65	75,334	93,999	98,327	Adipala	16	53271
33.01.07	Maos	34.30	40,410	46,188	47,100	Klapagada	10	53272
33.01.17	Sampang	28.89	36,636	43,426	44,754	Sampang	10	53273
33.01.06	Kroya	61.68	95,307	114,431	118,370	Kroya	17	53282
33.01.04	Binangun	53.73	54,574	68,684	72,026	Binangun	17	53280
33.01.05	Nusawungu	66.98	68,094	85,787	89,988	Nusawungu	17	53283
33.01.21	Cilacap Selatan (South Cilacap)	8.04	79,433	83,948	84,858	Sidakaya	5	53211 - 53215
33.01.22	Cilacap Tengah (Central Cilacap)	51.00	84,314	90,418	91,572	Gunungsimping	5	53221 - 53225
33.01.23	Cilacap Utara (North Cilacap)	29.72	69,265	82,630	85,315	Gumilir	5	53231 - 53235
	Totals	2,249.28	1,642,107	1,944,857	2,007,829	Cilacap Tengah	284

Notes: (a) except the desa of Cigintung (which has a post code of 53222) and the desa of Limbangan (which has a post code of 53232).
(b) includes the population but excludes the area (115 km) of the offshore island of Pulau Nusakambangan.
(c) consists of the 5 kelurahan of Cilacap, Sidakaya, Tambakreja, Tegalkamulyan and Tegalreja.
(d) consists of the 5 kelurahan of Donan, Gunungsimping, Kutawaru, Lomanis and Sidanegara.
(e) consists of the 5 kelurahan of Gumilir, Karangtalun, Kebonmanis, Mertasinga and Tritih Kulon.

The town of Cilacap is also a sea port on the southern coast of the island of Java. The port is one of only a few that exist on the southern coast that can service shipping of reasonable tonnage. The nearest safe anchorage east is Pacitan. The city's harbor is protected by Nusakambangan, an island best known as the site of several high-security correctional facilities although there are also hopes that the island can be developed as a tourist hub. Nusakambangan sheltered Cilacap from the worst of the 2004 tsunami. Nevertheless, the disaster took 147 lives, devastated beaches, damaged 435 fishing boats and inflicted material losses amounting to about Rp 86 billion (around $9 million).

During World War II Cilacap was an important departure point for people fleeing the Japanese invasion, especially Dutch colonists. Many left the Dutch East Indies by boat or seaplane, the majority heading for Broome in Western Australia.

The port is a hub for national or international trade. The town's Tunggul Wulung Airport provides scheduled airline services to Jakarta and Semarang.

Cilacap is the site of many industrial plants, a geothermal power plant, a cement plant (Holcim Indonesia), and one of Pertamina (Indonesia's national petroleum company) processing units in Indonesia. The site has the largest production capacity, producing the most diverse kinds of products among other Pertamina units.

The town of Cilacap offers several tourist attractions highlighting Banyumasan culture. The town has a number of beaches, two of the most popular being Teluk Penyu (close to the center of town), but these are somewhat fouled from leakage of the shipping vessels docked adjacent to this and Widara Payung. Nearby the Teluk Penyu beach is also an old Dutch fortress called Benteng Pendem. This fortress was built in stages during 1861-1879 by the Dutch East Indies Army.

In early 2012 Segara Anakan Bay's area is only 600 hectares, reduced from 700 hectares in 2005 after dredging. Heavy sedimentation from the Citanduy River (which is located on the border of Ciamis Regency and Cilacap Regency) caused it. To overcome the sedimentation in Segara Anakan Bay, Ciamis Regency has agreed, if a new canal from Citanduy River pass their area and exit in Nusawiru near Pangandaran Beach.

Cilacap has a tropical rainforest climate (Af) with heavy to very heavy rainfall year-round. The following climate data is for the town of Cilacap.

• 
  Cimandaway waterfall at district Dayeuhluhur, at Cikawalon River West Cilacap.

• Official website

7°44′S 109°0′E / 7.733°S 109.000°E / -7.733; 109.000