Jaak is a version of the name Jacob in Estonian language.
People named Jaak include:
Jaak Aab (born 1960), Estonian politician
Jaak Aaviksoo (born 1954), Estonian politician and physicists
Jaak De Boever (born 1937), Belgian racing cyclist
Jaak Boon (born 1948), Belgian television writer, director and producer
Jaak Gabriëls (born 1943), Belgian politician
Jaak Huimerind (born 1957), Estonian architect
Jaak Joala (1950–2014), Estonian singer
Jaak Jõerüüt (born 1947), Estonian writer and politician
Jaak Juske (born 1976), Estonian politician
Jaak-Nicolaas Lemmens (1823–1881), Belgian organist and composer
Jaak Lipso (born 1940), Estonian basketball player
Jaak Madison (born 1991), Estonian politician
Jaak Mae (born 1972), Estonian cross-country skier
Jaak Panksepp (born 1943), Estonian-American psychologist, psychobiologist and neuroscientist
Jaak Põldma (born 1988), Estonian tennis player
Jaak Salumets (born 1949), Estonian basketball player and coach
Jaak Tamm (1950–1999), Estonian politician and businessman
Jaak Urmet, better known as Wimberg (born 1979), Estonian poet and writer
Jaak Uudmäe (born 1954), Estonian triple jumper
Jaak van Velthoven, Belgian motocross rider
Jaak van Wijck (1870–1946), Dutch painter
