Lilla Värtan (Swedish: Smaller Värtan) or simply Värtan is a strait in Stockholm, Sweden. Separating mainland Stockholm from the island and municipality Lidingö, it stretches from Blockhusudden in the south to Stora Värtan in the north, and is joined by the Stocksundet mid-way. Two bridges, collectively called Lidingöbron ("Lidingö Bridge") stretch over the strait.
While most of the coasts surrounding the strait are occupied by industries and the ferry terminals and oil tanks in the harbour area of Värtahamnen, natural beaches are found in both the southern and the northern end of the strait and the strait forms part of the Royal National City Park.
The area is considered an important wintering location for several birds species, including swans, Eurasian coot, common pochard, tufted duck, black-headed gull, lesser black-backed gull, gadwall, and common tern. The strait constitutes an important locale, especially ice-free winters, besides the lake Isbladskärret on Djurgården.
- "Vattenvård : Sjöar och vattendrag : Lilla Värtan". Stockholm: Stockholms vatten. Archived from the original on March 16, 2005. Retrieved 2007-02-02.
- "Vattenprogram för Stockholm 2000 : Faktaunderlag : Lilla Värtan" (PDF). Stockholm: Stockholms vatten. Archived from the original (PDF) on March 16, 2005. Retrieved 2007-02-02.
- "Strandvegetation vid Lilla Värtan". Stockholm: Statens Fastighetsverk. Archived from the original on 2006-10-07. Retrieved 2007-02-02.
- "Totalfosfor - Kust och hav : Lilla Värtan". Stockholm: City of Stockholm. 2005. Retrieved 2007-02-02.