| Official Name: | Qayınsar |
| Native Name: | Каенсар |
| Native Name Lang: | tt |
| Settlement Type: | selo |
| Pushpin Map: | Russia Tatarstan |
| Subdivision Type: | Country |
| Subdivision Name: | Russia |
| Subdivision Type1: | Region |
| Subdivision Name1: | Tatarstan |
| Subdivision Type2: | County |
| Subdivision Type3: | District |
| Subdivision Name3: | Ätnä District |
| Subdivision Type4: | Municipality |
| Utc Offset1: | +3:00 |
Qayınsar (Tatar: Каенсар|translit=Qayınsar, Russian: Каенсар) is a rural locality (a selo) in Ätnä District, Tatarstan. The population was 119 as of 2010.[1]
Qayınsar, Atninsky District is located 12 km northwest of Olı Ätnä, district's administrative centre, and 87 km north of Qazan, republic's capital, by road.[2] [3]
The earliest known record of the settlement dates from 1646. Its name derives from the words qayın (birch) and the hydronym sar (swamp, from Finno-Ugric languages).[4]
From 18th to the first half of the 19th centuries village's residents belonged to the social estate of state peasants.
By the beginning of the twentieth century, village had a mosque and a mill
Before the creation of the Tatar ASSR in 1920 was a part of Çar Uyezd of Qazan Governorate. Since 1920 was a part of Arça Canton; after the creation of districts in Tatar ASSR (Tatarstan) in Tuqay (later Ätnä) (1930–1959), Tuqay (former Qızıl Yul) (1959–1963), Arça (1963–1990) and Ätnä districts.[5]