Jacen

Pronounced like Jay, this short name is popular in South Asia and makes for a great English-South Asian crossover choice, used regularly in the UK and Australia. It can also be an alternate spelling of the English name Jay, either short for a J name or deriving from the name of the bird.

 Famous bearers include Tamil-language actor Jai Sampath, Australian actor Jai Courtney, and American actor and musician Jai Rodriguez.

Jaina

Jannah

Jerek

Jessika

Julia was an ancient Roman imperial name given to females in the house of a Julius, as in Caesar. Its origin is shrouded in history, but possible roots include Latin iuvenis, meaning "youthfu"; Greek ioulos, meaning "downy-bearded"; or Jovis, a form of Jupiter, which means "sky father".
 
An enduring classic, Julia has a lot going for it: ancient roots but a modern, fashionable feel, simplicity and sophistication, and connections to both saints and celebs, including actress Julia Roberts and Saint Julia of Corsica. The elegant Julia's one of the least problematic choices a parent could make. 
 
Julia is also Shakespearean, Dickensian, Orwellian, and Harry Potter-related. The ground-breaking 1960s TV show Julia was the first to feature a non-stereotypical African American woman. Celebrity chef Julia Child is a notable namesake.
 
Julia has been in the US Top 150 since Social Security records have been kept and is currently the only <a href="https://nameberry.com/search/girls-names/j">girls' name starting with J</a> in the US Top 100. She's even more popular internationally, and is highly popular in the Netherlands in Spain, and in Germany, Belgium, France, Norway, and Sweden.
 
If you think Julia is too simple, you might want to move to Juliet, Juliette, or Juliana, or even the Italian Giulia. Sixties short form Julie has segued from cute to middle-aged. Jules is much more current.

Julia

A simple and charismatic Chinese and Korean name, also spelled Joon.

Jabba

Jango

Jarrus

Jinn

Jonner

Kanan is a popular name in the Middle East and one that is both rare and easily translated to the English speaking world.

Kanan

Kaydel is the name of the character played by Billie Lourd, the daughter of Carrie Fisher, in the 2017 Star Wars movie. There were no baby girls named Kaydel in 2016, but after the movie's release, we expect that to change. As with Kylo and Leia, Star Wars has a track record of introducing new names to the lexicon and promoting their popularity.

Kaydel

Actor Kit Harington, aka the dreamy Jon Snow on Game of Thrones, has given this nickname-name new style and appeal for boys. Actress Jodie Foster used it for her son. 
Kit is one of those names that is gender-neutral but has a different derivation for boys and girls. For boys, it originated as a short form of Christopher, while for girls, it's an updated diminutive of Katherine.
Kit as a full name is still beneath the Top 1000 for both sexes in the US, but it's getting more popular. In 2022, 166 baby girls and 137 baby boys were named Kit, up from 104 and 129 in 2021.

Kazuda

Kenobi

Ketsu

Ki-Adi

Koon

Koska

Kryze

Lively nickname, but we'd prefer the more substantial Orlando. 

Lando

Lars is a perfect candidate for a cross-cultural passport: it has been heard often enough here to sound familiar and friendly, yet retains the charisma of a charming foreigner.
 In this country Lars has been particularly associated with two Danes--Metallica's Lars Ulrich and film director Lars von Trier. In the 2007 movie Lars and the Real Girl, protagonist Lars Lindstrom was played by Ryan Gosling.

Lars

This spelling variation of Leya was popularized by the Star Wars films, but is still firmly in the US Top 1000 many years later. This spelling is also probably preferred as it is clearer in pronunciation to the original Hindi name, Leya (which sometime gets pronounced Lee-ah).

Leia

Luke is a cool-yet-strong Biblical name with a relaxed cowboy feel, which has been on the rise since the advent of Luke Skywalker.
 
Today, the Luke constellation of names is more popular than ever, with the ascendance of Top 10 Lucas and international star Luca. Luke ranks third in the group, but still stands in the US Top 50 and the Top 100 throughout the English-speaking world.
 
Luke originated as a short form of Lucas, a Latin derivation of the Greek name Loukas. The most famous bearer of the name is the first-century Greek physician—an evangelist and friend of Saint Paul, as well as the author of the third Gospel of the New Testament—who was also supposed to have been a portrait painter. He thus became the patron saint of doctors and artists.
 
Later Lukes have included Luke Duke of The Dukes of Hazzard, Cool Hand Luke, half of the classic soap opera duo of Luke and Laura, contemporary actors Luke Wilson and Luke Perry, and a number of star athletes.
 While Luke, Lucas, Luca, and the French Luc all have the same root and meaning, Lucius and Lucian have a different origin and meaning -- the more evocative "light".

Luke

Lux, one of the light-filled names that include Lucy and Lucian, broke onto the scene as a girls' name but now it's decidedly gender neutral. In fact, at the last count there were slightly more boys named Lux than girls: 140 to 120. But that's pretty close, making this a truly nonbinary name.

Lyra is a name with ancient and celestial roots that's finding new popularity thanks to its starring role in Philip Pullman's His Dark Materials series, seen in the movie The Golden Compass. Simple yet unique, Lyra hits the sweet spot between too popular and too unusual.
 
Lyra is a constellation name taken from the lyre of Orpheus. It contains the star Vega and thus could make a melodic choice for a parent interested in music, astronomy, or mythology. It has more depth and history than Lyric, is more unusual than Lila (which it rhymes with). It debuted in the US Top 1000 in 2015.
 Lyra was chosen for their daughter by Ed Sheeran and Cherry Seaborn, as well as Sophie Dahl and Jamie Cullum. And then there's Lyra Belacqua, the heroine of His Dark Materials and The Golden Compass.

Lyra

Larma

Latts

Lintra

Luminara

Carasynthia's list "Star Wars J-L Girl and Boy Names" of 34 great name ideas: Jacen - Luminara!