Kai
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Meaning
"sea" in Hawaiian; equally an independent name in Frisian and Scandinavian, Estonian, Japanese, and Chinese use, each with its own root and history. One crisp syllable that belongs everywhere, likely the secret of its global rise
Famously borne by Kai Lenny, the Hawaiian waterman who competes across nearly every ocean discipline.
The story
Kai is the Hawaiian word for the sea, and that alone would make a fine name, but Kai refuses to belong to one place: Scandinavians have used it for centuries, its origin there still debated, and Japanese and Chinese families know it with roots and meanings of their own. A name that several cultures each consider theirs is rare, and that, more than any celebrity, is likely the secret of its rise. In American records Kai surfaced in the 1980s and has climbed in every decade since, without a single pause, reaching its highest point yet in the 2020s and still pointed upward. One crisp syllable, open at both ends, easy to say in nearly any language on earth: in an age when families span oceans, Kai is the name that packs light and lands everywhere.
How popular is Kai around the world?
In the United States, 28,730 babies were named Kai between 2020 and 2025. In Ireland, 140 boys named Kai were born in 2025, the 34th most common name among boys that year.
Kai is on the official records of the United States, Ireland, Scotland, South Australia, Canada, England and Wales, Puerto Rico, New South Wales, Spain, New Zealand, Norway, Austria, Mexico City, Chile, Poland, Argentina, France and Brazil.
Kai crosses languages: it is in the latest top 300 of an English-speaking birth record and of a Spanish-speaking one. The full list: English and Spanish
United States
1 in 760
In the United States, 28,730 babies were named Kai between 2020 and 2025.
Shape drawn from US Social Security baby-name records. Kai peaked in the 2020s.
Births with a Social Security record. Source: U.S. Social Security Administration
Ireland
1 in 390
In Ireland, 140 boys named Kai were born in 2025, the 34th most common name among boys that year.
share of that year’s name registrations
Exact registered spellings from Irish vital statistics; any name under 3 in a year is withheld at source, and accented spellings (fadas) are recorded reliably only from 2018. Source: Central Statistics Office (Ireland), Irish babies' names
Scotland
1 in 540
In Scotland, 84 boys named Kai were registered in 2024, the 56th most common name among boys that year.
share of that year’s name registrations
Births registered in Scotland; different spellings count separately but accents are merged at source, and any spelling under 3 in total is suppressed. Source: National Records of Scotland, babies' first names
South Australia
1 in 5902017
In South Australia, 31 boys were registered as Kai in 2017.
share of that year’s name registrations
Births registered in South Australia (not all of Australia) by first name and year of registration, 1944–2017, from the state’s Births, Deaths and Marriages registry, which publishes every name down to a single birth in capitals; a spelling its export repeats inside a year is counted once, and from 2018 only a top 100 is published, so the series ends at 2017. Source: Consumer and Business Services (South Australia), popular baby names
Canada
1 in 760
In Canada, 468 boys named Kai were born in 2024, the 51st most common name among boys that year.
share of that year’s name registrations
First given names from provincial and territorial vital statistics across Canada; any name-sex-year under 5 is excluded at source, and small Quebec counts carry a randomized adjustment made at source. Shares divide by Statistics Canada’s count of live births for the year; the 2024 count is preliminary. Source: Statistics Canada, first names at birth (table 17-10-0147-01)
England and Wales
1 in 870
In England and Wales, 672 boys named Kai were born in 2025, the 78th most common name among boys that year.
share of that year’s name registrations
Birth registrations in England and Wales (not the whole UK); exact spellings are counted separately, and any spelling under 3 in a year is withheld at source. Source: Office for National Statistics, baby names in England and Wales
Puerto Rico
1 in 1,000
In Puerto Rico, 18 babies were named Kai in 2025, and 165 have carried the name since 1998.
share of that year’s births on record
First given name only, from Social Security records of births in Puerto Rico; any name-sex-year under 5 births is withheld at source. Shares divide by the Puerto Rico Demographic Registry’s count of births on the island; the 2025 count is provisional. Source: U.S. Social Security Administration, territory name file (Puerto Rico)
New South Wales
#23 · 2025
In New South Wales, 206 boys named Kai were registered in 2025, ranked 23rd in that year’s top 100 for boys.
share of that year’s top-100 registrations
New South Wales (not all of Australia) publishes only each year’s 100 most popular names per sex, so a missing year means below that top 100, not rare. Source: NSW Registry of Births, Deaths and Marriages, popular baby names
Spain
#91 · 2024
In Spain, 3,199 residents are named Kai, the 589th most common name among men, with a mean age of 9.5 years.
In Spain, Kai was the 91st most common name among boys born in 2024.
Residents of Spain on 1 January 2025. Spain publishes how old a name’s living bearers are, not a birth series, so there is no year chart. Source: INE (Spain), Censo de Población anual, 1 January 2025
New Zealand
1 in 1,700
In New Zealand, 34 boys named Kai were registered in 2025.
share of that year’s name registrations
First given names from New Zealand birth registrations, grouped by registration year; any name under 10 in a year is excluded at source. Shares divide by Stats NZ’s count of births registered to mothers living in New Zealand, under 1% below the registry’s own count. Source: Department of Internal Affairs (New Zealand), baby name popularity over time
Norway
1 in 2,000register 2026
In Norway, 14 boys were given the name Kai in 2025.
share of the boys on the register for that year, SSB’s own figure
People who have or have had a Norwegian ID number, emigrants left out, from Statistics Norway’s name statistics (release of January 2026): by year of birth for 1945–2020 (everyone born that year who was ever registered in Norway, including people who registered later and people who have since died) and by year of naming from 2021; only first names carried by 200 or more living people are listed, counts under 4 are withheld, and SSB merges spellings that differ only by letters outside the Norwegian alphabet. The shares are SSB’s own, of the people of that sex and year in that count; the 2025 figure counts the children named that year, and no year is a count of births. Source: Statistics Norway (SSB), table 10467 (updated 2026-01-28)
Austria
1 in 4,200
In Austria, 18 boys named Kai were born in 2025, the 305th most common name among boys that year, spellings that differ only by special characters counted together.
share of that year’s births on record
Live births in Austria by year of birth, 1984–2025, from Statistik Austria’s first-name statistics; spellings that differ only by special characters are counted together (umlauts stay apart), every name down to a single birth is published, and the count covers babies with Austrian citizenship only until 2009, every baby from 2010, and from 2015 also births abroad to mothers living in Austria. Shares divide by Statistik Austria’s count of live births from 2010, and before that by the file’s own total for the year. Source: Statistik Austria - data.statistik.gv.at (OGDEXT_VORNAMEN_1, updated 2026-07-09)
Mexico City City
1 in 4,900
In Mexico City, there were 24 registrations of Kai in 2022.
share of that year’s registrations in the city
Civil-registry acts in Mexico City by registration year. Counts are lower bounds (names under 6 in a month and borough are removed at source) and count name-instances, not people; compound names are split, so “Maria Jose” counts under each part. 2023 (2 registrations through 3 Mar) is excluded as partial. Source: Registro Civil of Mexico City, open data portal, registered given names 2000-2023
Chile
1 in 5,600
In Chile, 32 boys were registered as Kai in 2021, every accent spelling counted together.
share of that year’s name registrations
First-name registrations with Chile’s civil registry by year of registration, 1920–2021, counted as spelling groups (Sofía, Sofia and Sofìa are one name, shown with its most-registered spelling); the registry withholds nothing, nametree keeps the groups that reached 5 registrations in some year, and shares divide by every registration of the year. Source: Servicio de Registro Civil e Identificación (Chile) via the guaguas package, first-name registrations 1920-2021
Poland
1 in 6,200
In Poland, 40 boys named Kai were born in 2025, the 195th most common name among boys that year.
share of that year’s name registrations
First names given to children born in Poland by year of birth, 2000–2025, from the PESEL population register (Ministry of Digital Affairs); exact spellings count separately (Łukasz and Lukasz are different names), names given fewer than 5 times in a year were left off the list through 2012 and fewer than 2 times from 2013, and the register also counts children born abroad, so its yearly sums run above Poland’s live births. Shares divide by the register’s own published total for the year, never by births. Source: Ministry of Digital Affairs, PESEL register (dane.gov.pl)
Argentina
1 in 12,000
In Argentina, 57 newborns were given the name Kai in 2024.
share of that year’s name registrations
Given-name components of births in Argentina 2012–2024; national cells are lower bounds and no sex split is published. Source: RENAPER (Argentina), Dirección Nacional de Población, given names 2012-2024
France
1 in 18,000
In France, about 35 boys named Kai were born in 2025, ranked 1,050th among boys that year.
share of that year’s births on record
Births in France by year of birth, from INSEE’s fichier des prénoms (1900–2025; Mayotte from 2012); exact spellings count separately (Léo and Leo are different names), any spelling under 3 in a year and sex is withheld at source, every count is rounded to the nearest 5 at source, and nametree keeps the spellings that reached 20 in some year. Shares divide by INSEE’s count of births in France from 1957, and before that by the file’s own total for the year; INSEE says the file is not complete before 1946. This registry counts each spelling separately; the figures above are for the exact spelling Kai, and accented spellings are separate names. Source: Insee, fichier des prénoms (last updated 2026-07-16)
Brazil
1 in 500,000
At the 2022 census, 319 people in Brazil were named Kai, ranked 18,217th, with a median age of 9.
Among people named Kai living in Brazil at the 2022 census, more were born in the 2010s than in any other decade.
people alive at the 2022 census, by decade of birth
The census also counted 92 born between 2020 and August 2022, too recent a span to chart. People alive and resident in Brazil at the 2022 census, a living-population count, not births; names under 20 are withheld at source. Source: IBGE, Censo Demográfico 2022
Montevideo City
last on record 1997
Kai is not on the 2011 record for Montevideo, whose registry withholds nothing, so the spelling was not given there that year.
The count never rose above 1 in a year, too few to chart.
Births in the department of Montevideo (not all of Uruguay) by first name and year of birth, 1940–2011, from the city’s civil registry, which writes names in capitals, almost always without accents; counted as spelling groups (accent and punctuation variants merged), nothing is withheld at source, and 2012 is excluded as a partial year. Source: Servicio de Registro Civil, Intendencia de Montevideo, Partidas de Registro Civil de Montevideo (Licencia de Datos Abiertos - Uruguay); 2012 dropped as partial
When you meet Kai
Most people given the name Kai in the United States are children or teenagers today. The name belongs to this generation.
Estimated from US Social Security birth registrations and typical lifespans; a rough guide, not a rule.
The meeting point
Five unrelated language families arrive at the same three-letter name.
Kai · a Frisian and German name of its own; its origin is uncertain, possibly a diminutive of Gerhard, Nicolaas, Cornelis or Gaius
Kaia · an Estonian feminine name, the short form of Kaia
Kai · "sea" in Hawaiian
Kai · triumph when written 凯 or 凱 in Chinese; other characters spell other names that sound the same
Kai · ocean (海) in Japanese, a spelling path of its own; no historical link to the Hawaiian name is documented
Nicholas · sources also list Kai among the northern forms of Nicholas, in Danish, Dutch, German and Norwegian
Where Kai travels
Dual-language · also a genuine Japanese name (海, or 甲斐, an old place-name reading) and a common Cantonese/Hong Kong English name from characters like 啟 or 凱; one of the strongest three-way East Asian/Pacific/English crossovers going
Global crossover · sea (also a Japanese, Frisian and Scandinavian name); popular in Germany and the Netherlands and one of the fastest-rising names in the US
Keep exploring
Names like Kai · Names that go with Kai · Middle names for Kai · Hawaiian baby names · Dual-language baby names · Global crossover names · Japanese baby names · Short names · What is Kai short for? · Gender-neutral names
The Kai deep dive
Whether you’re naming a baby or exploring your own name’s history, this is a personal letter, not a list: where Kai truly comes from, how it traveled, and what a century of records reveals. If you have grown a tree on nametree, it also considers how Kai fits with your family’s names and surname.
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