How to say it
ka · SAI
kɑːˈsaɪ
Masculine
Kasai
River name; Japanese surname
What it means
A name shared by the Kasai River of Central Africa and by Japanese surnames such as 笠井 and 河西.
Kasai has two unrelated sources that happen to land on the same sound. In Central Africa it is the name of the Kasai River, a major tributary of the Congo, and the surrounding regions in the Democratic Republic of Congo and Angola, drawn from Bantu languages. In Japanese it is a family name written several ways, most commonly 河西 ('west of the river') or 笠井 ('bamboo-hat well'). The two traditions developed independently, so the meaning depends entirely on which one a family has in mind. Kasai entered the US top 1000 in 2025 as a fresh, open-vowel pick.
How to spell Kasai
Spelled Kasai. K · a · s · a · i — 5 letters total.
Popularity over time
peaked at #639 in 2025, currently #639 in 2025.
Source: U.S. Social Security Administration, names given to at least 5 babies in a year, 1880–2025. Reviewed July 2026. See where the names are moving
Heads-up notes
- Pronunciation
kah-SIGH, two syllables.
- Spelling
African river name and Japanese surname are separate roots that share the spelling.
Names with the same feeling
See Kasai from another angle
By meaning
By style
Common questions
- What does the name Kasai mean?
- A name shared by the Kasai River of Central Africa and by Japanese surnames such as 笠井 and 河西.
- What does Kasai mean in Japanese?
- In Japanese, Kasai means "River name; Japanese surname." Kasai has two unrelated sources that happen to land on the same sound. In Central Africa it is the name of the Kasai River, a major tributary of the Congo, and the surrounding regions in the Democratic Republic of Congo and Angola, drawn from Bantu languages. In Japanese it is a family name written several ways, most commonly 河西 ('west of the river') or 笠井 ('bamboo-hat well'). The two traditions developed independently, so the meaning depends entirely on which one a family has in mind. Kasai entered the US top 1000 in 2025 as a fresh, open-vowel pick.
- How do you pronounce Kasai?
- Kasai is pronounced kɑːˈsaɪ. Say it as ka-SAI, with the stress on the "sai" syllable.
- How do you spell Kasai?
- The name is spelled K-a-s-a-i.
- Is Kasai a boy or girl name?
- Kasai is traditionally a masculine name.
- How popular is the name Kasai?
- Kasai ranked #639 in the U.S. in 2025, according to Social Security Administration data.