| Official Name: | Klein-Sinaai |
| Settlement Type: | Village |
| Pushpin Map: | Belgium |
| Pushpin Label Position: | left |
| Pushpin Map Caption: | Location in Belgium |
| Pushpin Mapsize: | 250 |
| Subdivision Type: | Country |
| Subdivision Type1: | Region |
| Subdivision Type2: | Province |
| Subdivision Type3: | Municipality |
| Subdivision Name: |  |
| Subdivision Name1: | Flemish Region |
| Subdivision Name2: | East Flanders |
| Subdivision Name3: | Stekene |
| Area Total Km2: | 4.70 |
| Population As Of: | 2021 |
| Population Footnotes: | [1] |
| Population Total: | 1,381 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Coordinates: | 51.1802°N 3.9879°W |
Klein-Sinaai is a village near the Dutch border in the Belgian municipality of Stekene in the province of East Flanders. Until 1977 it was a part of the municipality of Sinaai.[2]
In Klein-Sinaai are the remains of (also known as Boudeloo Abbey), formerly a monastery of the Cistercians.The abbey was founded in 1197 when, a monk from St. Peter's Abbey in Ghent, settled in Klein-Sinaai as a hermit. In the early 13th century the abbey was recognised by the Bishop of Doornik. In 1578 the abbey was destroyed by Calvinists from Ghent, but was rebuilt a few years later, within the walls of Ghent itself.[2]
The museum of cultural history in Sint-Niklaas exhibits several archaeological finds from Boudelo Abbey.
In 1877, a railway station opened on the Sint-Gillis-Waas to Zelzate railway. The line closed for passengers in 1952 and the track was removed in 1974.[3]