Osiek [ˈɔɕɛk] is a town in Staszów County, Świętokrzyskie Voivodeship, Poland, with 2,001 inhabitants (2010). The town lies in Lesser Poland, along the National Road nr. 79, which goes from Warsaw to Bytom. Osiek is located 15 kilometers northeast of Połaniec, and 18 kilometers west of Tarnobrzeg, 180 meters above sea level.

Its main point of interest is St. Stanisław parish church, built in the late 17th century. Osiek has a rail station called Osiek Staszowski, on a secondary importance line which joins Tarnobrzeg with Włoszczowice.

Osiek is one of the oldest towns in the region. According to legends, in 1020 King Bolesław Chrobry presented the village called Ossziek to the Benedictine Monastery at Święty Krzyż. In 1253 the name of the village was spelled Ossek. It belonged to Princes of Sandomierz, and had its own marketplace. In 1270, Osiek was the property of Prince Bolesław V the Chaste. Its residents took advantage of a favorable location, along a merchant route from Kraków, through Sandomierz and Lublin, to the Grand Duchy of Lithuania. Many Piast dynasty princes would stop here during their trips across the country. Osiek most likely was a fortified gord, and in the mid-14th century, King Casimir III the Great built (or strengthened) a local castle.

Osiek was burned in the Second Mongol invasion of Poland, but the village was quickly rebuilt. In 1430, King Władysław II Jagiełło granted it the Magdeburg rights, allowing the town to organize weekly markets on Wednesdays. Osiek was a royal town of the Kingdom of Poland, administratively located in the Chęciny County in the Sandomierz Voivodeship in the Lesser Poland Province. It prospered during the Polish Golden Age. In the second half of the 16th century, its population amounted to 1,000, with a number of guilds, such as bakers, butchers, blacksmiths, tailors, potmakers, and millers. Osiek had 100 houses, and a wooden parish church of St. Stanisław. The decline of the town was brought by the Swedish invasion of Poland (1655–1660). Like almost all Lesser Poland's towns, Osiek was ransacked and burned, and never recovered from the destruction.

Following the Third Partition of Poland, in 1795, it was annexed by Austria. After the Polish victory in the Austro-Polish War of 1809, it was regained by Poles and included within the short-lived Duchy of Warsaw. After its dissolution, since 1815, it was part of the Russian-controlled Congress Poland. The town further declined in the 19th century, losing its charter in 1869, after January Uprising.

During the Invasion of Poland (September 1939), retreating units of the Polish Army fought here a battle with the Wehrmacht, in which app. 100 Poles died. As a result of World War I and World War II destruction, there are no other historic buildings in Osiek, except for the parish church.

On 1 July 1994 Osiek regained its town rights.

According to the 2011 Polish census, there were 2,001 people residing in Osiek, of whom 50% were male and 50% were female. In the town, the population consisted of 21.2% inhabitants under the age of 18; 38.6% between the age of 18 and 44; 23.6% from 45 to 64; and 16.6% residents who were 65 years of age or older.

Table 1. Population level in 2010 – by sex

SPECIFICATION						Measure unit	POPULATION (by sex in 2010)
							TOTAL	Males	Females
I.	TOTAL					person	2,001	1,000	1,001
	—	of which in				%	100	50	50
	1.	BY AGE GROUP
		A.	At pre-working age			person	425	215	210
			—	of which in		%	21.2	10.7	10.5
		B.	At working age, grand total			person	1,244	659	585
			—	of which in		%	62.2	33	29.2
			a.	at mobile working age		person	772	384	388
				—	of which in	%	38.6	19.2	19.4
			b.	at non-mobile working age		person	472	275	197
				—	of which in	%	23.6	13.8	9.8
		C.	At post-working age			person	332	126	206
			—	of which in		%	16.6	6.3	10.3

Table 2. Population level in 2010 – by age group

SPECIFICATION					Measure unit	POPULATION (by age group in 2010)
						TOTAL	0-4	5-9	10-14	15-19	20-24	25-29	30-34	35-39	40-44	45-49	50-54	55-59	60-64	65-69	70-74	75-79	80-84	85 +
I.	TOTAL				person	2,001	116	81	141	145	143	151	157	150	113	141	150	128	101	81	61	58	50	34
	—	of which in			%	100	5.8	4	7	7.3	7.1	7.6	7.8	7.6	5.6	7	7.6	6.4	5	4	3	2.9	2.5	1.8
	1.	BY SEX
		A.	Males		person	1,000	55	44	77	65	67	82	79	80	50	77	82	63	53	47	21	17	24	17
			—	of which in	%	50	2.8	2.2	3.8	3.2	3.3	4.2	3.9	4.1	2.5	3.8	4.2	3.1	2.6	2.3	1	0.9	1.2	0.9
		B.	Females		person	1,001	61	37	64	80	76	69	78	70	63	64	68	65	48	34	40	41	26	17
			—	of which in	%	50	3	1.8	3.2	4.1	3.8	3.4	3.9	3.5	3.1	3.2	3.4	3.3	2.4	1.7	2	2	1.3	0.9

In the years 1970 of last age, sorted and prepared out list part of names of localities for Osiek, at as type of settlement then yet is a village, what you can see in table 3. Remaining not exchanged parts here are described in integral part of town Osiek now, in Osieczko.

Table 3. Index of official names of localities and physiographic objects

Names of village – town	Names of part of village – town	Names of physiographic objects – nature of objects
I. Gromada OSIEK
Osiek	Dwór Gaj Osiecki Grabowiec Parysówka	Broźnia – forest Buchnia – field Chudyniówka (Chudzyniówka) – field Dołki – field Gaj Osiecki – field Grabowiec – field, forest Kacapówka – field, forest Kozłówka – meadow Ługi – field Nakielec – field Niwa – field Parysówka – field Pasierbowskie – field Pastwisko – meadow Pod Cmentarzem – field Pod Kierkutem – field Pod Wolą – field Podgórki – field Posusze – field Rzeka – brook Skotnia – field Stawiska – meadow Zagrądzie – field Zagroble – meadow, field Zagumnie – field