Olaine (pronunciation; German: Olai) is a city in Olaine Municipality in the Vidzeme region of Latvia. Olaine gained town rights in 1967. The population in 2020 was 10,668.

The name comes from the Saint Olaf Church [lv] (Swedish: Sankt Olai kyrka), built by the Olainīte [lv] stream, a Misa river tributary, under Swedish rule in the 17th century, at a place which is within the village now known as Jaunolaine [lv] ("New Olaine") some two kilometers away from the modern Olaine. An old cemetery remains at this site. After 1868, a railway stop "Olai" (now the Jaunolaine Station) was built here on the Riga-Mitau line. After Latvian independence, in 1919 "Olai" was renamed to "Olaine", in line with the Latvianisation of place names all over Latvia.

The history of modern Olaine is associated with the works at nearby peat bogs, taken into use on an industrial scale in 1939. Thereafter, more production facilities were built, increasing numbers of workers needed accommodation, and the first dwellings were built in what is currently known as Olaine in 1940. As of 2023 local peat processing is handled by the "Olaines kūdra" Ltd. ("Olaine Peat" Ltd.), a private company centrally managed together with 4 other Latvian peat companies by the German company “Kudras Substrates – Peat Moss”.

Olaine is home of Olpha, the second largest pharmaceutical company in Latvia.

Olaine is twinned with:

• Rustams Begovs - Latvian hockey player
• Žaneta Jaunzeme-Grende - Latvian politician
• Dmitrijs Miļkevičs - Latvian athlete
• Jānis Kuzmins - World champion in slalom skateboarding

• Vilīte, Valda: Olaines pagasts (2008)

• List of cities in Latvia