Kaynardzha (also transliterated as Kajnardža; Bulgarian: Кайнарджа, IPA: [kɐjnɐrˈd͡ʒa]; Romanian: Cainargeaua Mică; Turkish: Kaynarca; Greek: Καϊναρτζή) is a village in northeastern Bulgaria, part of Silistra Province.

It is the administrative centre of Kaynardzha Municipality, which lies in the easternmost part of Silistra Province, in the historical region of Southern Dobruja, close to the Romanian border.

The village is known as the location of the signing of the Treaty of Küçük Kaynarca on 21 July 1774 between Count Pyotr Rumyantsev, representative of Empress Catherine the Great of the Russian Empire and Musul Zade Mehmed Pasha, representative of Sultan Abdul Hamid I of the Ottoman Empire.

After the Balkan Wars, it was ceded by the Kingdom of Bulgaria to the Kingdom of Romania along with all of Southern Dobruja; as part of the interwar Durostor County, it was known as Cainargeaua Mică, a translation and adaptation of the older Ottoman Turkish name, Küçük Kaynarca ("small spa place").

Since October 2017, Kaynardzha has been linked with the neighbouring commune of Lipnița in Romania via the Kaynardzha-Lipnița border crossing.