Lake Haruna (榛名湖, Haruna-ko) is a caldera lake. It lies near the summit of Mount Haruna, within the city limits of Takasaki, Gunma Prefecture, Japan. A former name for the lake is Lake Ikaho (伊香保沼, Ikaho-numa).

Lake Haruna
The Fuji of Haruna Adolfo Farsari
Lake Haruna
Location	Takasaki, Gunma
Coordinates	36°28′30″N 138°52′0″E / 36.47500°N 138.86667°E / 36.47500; 138.86667
Type	caldera
Basin countries	Japan
Surface area	1.15 km2 (0.44 sq mi)
Max. depth	12.6 m (41 ft)
Shore length1	6 km (3.7 mi)
Surface elevation	1,084 m (3,556 ft)
1 Shore length is not a well-defined measure.

In the summer, the lake is a popular destination for campers. The surface freezes in the winter, and it affords skating and ice fishing for wakasagi.

The lake lies a 90-minute bus ride from Takasaki Station. It can be reached in 40 minutes by car from Shibukawa-Ikaho Interchange, #12 on the Kan-Etsu Expressway. The road to the lake is one of 10 musical roads located in Gunma prefecture alone; the song played is "Sweetly Sings the Donkey," chosen because the melody is known as "At a Quiet Lakeside" in Japan.

A kayōkyoku refers to the lake in its title. Akira Fuse recorded the tune, named Haruna-ko no shōjo. The music is by Rei Nakanishi and the lyrics by Ken'ichirō Morioka.

Parts of the anime and manga Initial D take place on or around the lake, under the fictional name Lake Akina, as Mount Haruna - named Akina (秋名) in the series - is the location of the tōge where Takumi, the protagonist, wins his first races.