"She's got the whole world in her head!"
— Dr. Xeno, Chapter 172
Chelsea Childe (チェルシー・チャイルド Cherushī Chairudo) is a geographer that was found alone in North America.
Chelsea is a young woman with a ponytail ending in pronounced swirls. She has short bangs that are swept outward in both directions, with smaller pieces of hair sticking out in front of her ears. She has wide, round, cutesy eyes and her upper lip seems to always be in a '3' shape.
Initially, Chelsea was dressed in a large pumpkin, similar to Suika's helmet. She used it to store her tools in. In addition, Chelsea has the "fuzzy sickness", resulting in a terrible squint.
Soon after meeting, Senku and the others create a set of glasses for her, also outfitting her with a generic explorers outfit consisting of shorts, a large belt, and a jacket with rolled sleeves and several pockets. She replaced her singular large pumpkin with a smaller one smashed over her pith helmet, and another medium-sized pumpkin as a knapsack. A smaller pumpkin rests on her belt, presumably to act as another container. She also wears a whip on her hip. Her socks are pulled up to just below her knees, and her ankle boots have a single button clasp with no laces.
Chelsea is a happy girl who seems friendly and excited, especially after seeing people for the first time after petrification. She also insists she is "besties" with Dr. Xeno after bumping into him in the national park prior to the petrification event, which might show it doesn't take much to befriend her.
While Chelsea is generally enthusiastic and composed by most things she has shown a comedic shock as seen when she freaked out by Senku suggesting they create a fax machine.
Her straightforward and carefree attitude when talking earns her a nickname of "Chelsea the Blunt" by Gen when she ask Luna directly about her weight. This makes her seem a little rude when combined with her tendency to point at people.
In alignment with her amicable personality, Chelsea opposes Xeno's ideas of ruling the world with an iron fist.
Chelsea is a skilled geographer and appears to be able to identify rocks such as sphalerite.
She possesses a strong will, as she was able to stay conscious during her time petrified. Despite suffering from nearsightedness, she was able to endure for a year while completely alone in the wilderness, showing excellent survival skills and the ability to make her own shelter and distress beacon.
Prior to the petrification, Chelsea was a "genius teen geographer" and throughout her life did much high level research. At some point, she is awarded a doctorate for her work while still only 18! She was invited to the summit to discuss the swallow petrification thanks to her expertise.
In the year 5741, Chelsea broke out of her petrified state three years later than Xeno did for unknown reasons, in the middle of a pumpkin patch. She found the sign Xeno left directing her north, though due to her lack of glasses she was unable to read the sign and made the choice to follow the coast southward, as she incorrectly assumed the group would aim to go to California's orange groves. Regardless, Chelsea manage to survive in the wilderness for over a year and survived in a pumpkin hut.
Taiju was the first one she made contact with after flying several large kites with letters spelling H-E-L-P on them in phosphorescent paint made of sphalerite pebbles. Unfortunately, she failed to notice that she ran out of paint on the 'P' and ended up spooking Taiju by writing H-E-L-L. This caused him to believe that the Why-man was around. The morning after, Chelsea's hanging pumpkin hut was found by the group. After seeing her scary squinting expression, Suika realized that she needed glasses. Hearing Suika's exclamation alerted Chelsea to the presence of other humans, causing her to cry with relief. Once cleaned and dressed, Chelsea is given a new set of glasses and is excited that she can see again. She and Xeno soon recognize each other and he described her to everyone. Chelsea then gives a little of her history and is dismayed by everyone criticizing what choice she made to go in direction. Senku explains their plan to get to the other side of South America without Stanley catching them. After some thought, Chelsea points out a location that would allow them to cut across via landing in northern Ecuador, climbing a mountain, then using the Amazon river the rest of the way. She recommends using a motorcycle for the land-based part, as "that quick trek is basically a death sentence." Obviously, as the Kingdom of Science do not currently have a motorcycle, Senku took this as a challenge and started the next roadmap.
During the voyage, Chelsea is updated by Gen on the recent events like Why-man, their recent fleeing from Stanley, and the reason for the journey. After getting the gist of the situation, she excitedly calls Xeno a "bad guy" and decides to join Senku's group after refusing his offer. Very soon, the crew face a problem when the Perseus nearly catches up. When making Chelsea remarks on her kites, the group use them as sails elude the enemy at a faster pace.
The team continued to sail, while knowing they were still being pursued by Stanley's forces on the Perseus. Deciding they need to collect rubber for motorcycle tires in order to cross South America. Chelsea makes a comment that she wishes the Panama canal was still viable, prompting Francois to explain to everyone what the canal was. After Taiju becomes excited at the prospect of being able to use it, Chelsea remarks it's probably been filled in over the last few centuries. Needing a decoy to lure Stanley away, they cast off the amphibious Mobile Lab, decorated in metal to be better seen by the radar on the Perseus, sending it in the direction of the canal on 'autopilot' (they tied the controls). The rubber team then land on the shore, following Chelsea's advice. Sure enough, they find rubber trees which they immediately start tapping. Using the rubber resin, adding vinegar and sulfur powder and then kneading and forming the result, the team produce several bouncy rubber balls. The group is pleased with rubber having been acquired.
Chelsea and Luna are fascinated by the others playing with rubber. Chelsea later watches the group create tires for the soon to be invented vehicles. She excitedly tells everyone they made it to Ecuador and if this is where they depart from the small ship. Chelsea remarks on how Ecuador has now become a barren desert over the last few millennia. Soon they are told by Ukyo, Stanley will be soon approaching them now at the mobile lab has been sunk in it they don’t have a moment to spare and creating motorcycles. Some time later, the Perseus appears at the shore, though Chelsea and her allies were able to complete the task. Riding with Senku and Gen, they make their escape from Stanley and his unit.
While riding away, the group are shot at by the soldiers but evade the bullets. Chelsea soon comments on how brutal Hyoga is after he casually uses Xeno as a shield to prevent enemy attacks.
Chelsea helps Senku with creating a map for geographic layout of the Stone World, much to everyone's amazement. When it is mentioned that they would not reach America, Chelsea is surprised when Senku recreates the fax machine. 
When making a stop in the mountains, Chelsea makes more blunt remarks about Senku and Luna's status, Luna's weight while being horrified to learn about Hyoga potentially being duplicitous. However, she is overly excited about the idea of crafting a ropeway.
When Suika and Francois were captured, Chelsea was able to pinpoint the enemy location.
Chelsea and Luna were chosen as the backup revival team. As they move out, Chelsea suffers an emotional breakdown while realizing everyone's efforts might be in vain. Her reaction causes Luna to nearly head back to the Fort, though they see it has already come under attack. 
While on the hill, Chelsea spotted the Petrification beam over the horizon and realized what was about to happen. They made a plan to throw a bottle of Revival Fluid upwards so they can revive. However, because of Luna's poor toss, the bottle curves and hits the ground, to their horror. Chelsea and Luna ended up petrified.
Three years later, her petrified statue is located by Suika who revived earlier. Suika discovered the shattered bottles of formula and found Chelsea still on the hill with Luna. Chelsea was placed with her other collected allies.
Four years pass, with Suika being able to revive Senku who completed the formula and revived everyone, Chelsea included. An overjoyed hugged the now older Suika before watching everyone else revive. She nudges Hyoga to say something after he is revived and he begrudgingly complies. She watched as Tsukasa and Hyoga later hunted several animals and used their pelts to make new outfits for everyone. That night, she joined the others at the celebration. 
When needing to build superalloy, Chelsea joins the others in dismantling the Perseus and tells the sulking Kaseki that she needs its terrible but they need iron. However, Senku states they will rebuild it into something better, something that excites him. After several days of construction, Superalloy City is finished and many people are revived to inhabit. 
While building the new ship, Chelsea brings up how South America lacks oil that is required to fuel the ship. However, Senku easily resolved this by stating they will use biofuel instead. When the new Perseus is functional, it was decided that the group would have to split into three teams if they want to succeed in reviving the whole world. Chelsea is placed with the group that travel the world while collecting materials: Senku, Chrome, Kohaku, Suika, Ryusui, Francois, Kaseki, Gen and Suika.
- Chelsea appears to have no visible petrification marks.
- For her age, she states she is "barely [still] a teen" (ギリ10代 giri jū-dai).
- Senku comments that she reminds him of Chrome, since she was also "all about field research" and collected rocks.
- Her debut chapter came out in late October around Halloween, which may have been an inspiration for her pumpkin motif.
- She was also revived near the birthplace of pumpkins, in southern United States.
- Chelsea is the only character to wear socks after the petrification event.
- Chelsea's design pays homage to other famous explorers, especially Indiana Jones as she carries his signature whip as well.
- Unlike some of the Americans, Chelsea had no problem in communicating with those of the Kingdom of Science.
- Much like Xeno and Senku, Chelsea too has does a hand motion when in thought.
- Xeno crosses his fingers, Senku puts two fingers together, and Chelsea does an OK symbol when in thought.