Lake Elgygytgyn, also transcripted El'gygytgyn, (Russian and Chukchi: Эльгыгытгын) is a crater lake in Anadyrsky District, Chukotka Autonomous Okrug in northeast Siberia, about 150 km (93 mi) southeast of Chaunskaya Bay.

The word "Elgygytgyn" means "white lake" in the Chukchi language.

The lake is of particular interest to scientists because it has never been covered by glaciers. This has allowed the uninterrupted build-up of 400 m (1,300 ft) of sediment at the bottom of the lake, recording information on prehistoric climate change.

Lake Elgygytgyn is an impact crater lake located in the Anadyr Plateau, part of the Anadyr Highlands. It is drained to the southeast by the Enmyvaam, a tributary of the Belaya. It is approximately 12 km (7 mi) in diameter and has a maximum depth of 174 ± 2 m (571 ± 7 ft). The lake is centered within an impact crater with a rim diameter of 18 km (11 mi) that formed 3.6 million years ago during the Pliocene. Before it was reliably dated, preliminary papers in the late 1970s suggested either Elgygytgyn or Zhamanshin as the source of the young Australasian strewnfield.

In late 2008 and early 2009, an international team conducted a drilling program targeting three holes in Elgygytgyn Lake. The resulting cores are designated ICPD Site 5011-1 and 5011-3.

The conditions in Elgygytgyn lake are extremely severe for fish life, being classed as an ultra-oligotrophic lake and the surface covered by ice for around 10 months of the year. Even so, there are three species permanently inhabiting the lake's harsh aquatic environment, all species of char. These are Salvelinus boganidae (Boganid Char), S. elgyticus (Small-mouth Char) and Salvethymus svetovidovi (Long-finned Char). The two latter species are endemic to the Elgygytgyn lake. All three species are adapted to the lake's extremely cold waters, which are generally just above the freezing point, and spend most of the year in total darkness. It may start to melt in the summer, but some years it never fully thaws. The lake is also home to more than a dozen endemic diatoms.

• List of lakes of Russia

• Dr. Matt Nolan at the University of Alaska Fairbanks
• Polar Expedition to Siberian Lake will Yield Details of Past Climate PhysOrg.com.
• NASA Earth Observatory
• Haltia E. M., Nowaczyk N. R. Magnetostratigraphy of sediments from Lake El’gygytgyn ICDP Site 5011-1: paleomagnetic age constraints for the longest paleoclimate record from the continental Arctic, 2014.