Straw Hat Pirates/Allies

Throughout the series, there have been people who either traveled with one or all of the Straw Hat Pirates for a short period of time or aided them in one way or another. Many of these individuals would be considered temporary pirates in a way. Along with those individuals, there have also been various groups that have assisted the Straw Hats in their adventures. These groups have helped the Straw Hats either to reach a certain goal or to defeat a common enemy.

Straw Hat-Galley-La-Franky Family Alliance
An alliance formed on the way to Enies Lobby to rescue Nico Robin and Franky from the World Government, as well as retaliate against CP9 for the assassination attempt on Iceburg. The majority of the help occurred in the courtyard and courthouse in order to help the Straw Hats reach the Tower of Justice and face the CP9 agents, with the Franky Family entrusting the rescue of their leader to the pirates. The allies went their separate ways when the Straw Hats continued their journey with Franky as their new Shipwright, and the Franky Family started working for Iceburg and the Galley-La Company. This alliance is aided by Kokoro, Chimney, Gonbe, Yokozuna, Oimo, Kashi, Iceburg and Usopp under the alias "Sogeking".

Straw Hat-Heart Alliance
An alliance between the Straw Hat Pirates and the Heart Pirates formed on Punk Hazard by their two captains in order to defeat Kaido, one of the four Yonko of the New World. According to Law, who proposed the alliance, their cooperation would give them a 30% chance to defeat the Yonko. The plan was to destroy Kaido's source of SMILE delivered by Doflamingo, weakening him while letting Doflamingo take on Kaido's anger. However, the events on Dressrosa made Law concerned about Kaido's reaction. This alliance is aided by Kin'emon, Momonosuke, Kanjuro, and an unwilling Caesar Clown, and briefly by the G-5 marines under Vice Admiral Smoker and Captain Tashigi, the kidnapped kids used for Caesar experiments, and Brownbeard on Punk Hazard, and by the Corrida Colosseum fighters including the Straw Hat Grand Fleet members, Elizabello II, Dagama, the Riku Family, the citizens of Dressrosa and Green Bit, a representative of the Revolutionary Army, and Admiral Fujitora on Dressrosa. The alliance eventually would grow to became the "Ninja-Pirate-Mink-Samurai Alliance" on Zou.

Ninja-Pirate-Mink-Samurai Alliance
An alliance of the Kozuki Family retainers with the Straw Hat-Heart Alliance formed on Zou in response to Momonosuke's request for the pirates to help him avenge his parents against the Beasts Pirates and the shogun of Wano Country and release Wano from their control. The alliance attack is postponed until the Sanji rescue mission from the Big Mom Pirates is completed. Nekomamushi has shown interest in finding and recruiting Marco and the remaining Whitebeard Pirates. This alliance is aided by the entire Mink Tribe, through its leaders, Zunisha, and the Kozuki Family allies and rebels from Wano.

Sanji Retrieval Team-Fire Tank Alliance
An alliance formed between the Sanji Retrieval Team and the Fire Tank Pirates. Both groups agreed to work together during Big Mom's Tea Party, the main event of which will be the wedding ceremony between the Germa Kingdom's third prince (and the Straw Hats' cook), Vinsmoke Sanji, and Big Mom's 35th daughter, Charlotte Pudding. While the two groups share a common opposition to Big Mom, they have slightly different goals: The Straw Hats want to prevent Big Mom's planned assassination of Sanji and his family during the event, while Capone Bege, Captain of the Fire Tank Pirates, wants to use the opportunity to take down Big Mom herself. The alliance was offered by Jinbe after hearing of both wedding day conspiracies from Pekoms, who was targeted by the Fire Tank Pirates, and Brook, who was present when Pudding and Big Mom discussed their plans. The alliance is supported by Jinbe and the Sun Pirates, Charlotte Chiffon, Bege's wife and Big Mom's 22nd daughter, an unwilling Caesar Clown, and Big Mom Pirates members Charlotte Brûlée and Diesel. The Vinsmoke Family later joined the allied forces as Big Mom's true intentions was revealed to them, and Brûlée was rescued by her brother. After the collapse of the Whole Cake Chateau, the alliance managed to escape. The alliance disbanded and each group went their separate ways. The Straw Hats split to retrieve their Shark Submerge III and the rest headed to the Thousand Sunny. The Fire Tank Pirates were inside Bege as he fled. Caesar left after he was given back his heart. Even after the crews separated, they still have a friendly relationship as Vito and Chiffon complained about not being able to say goodbye, followed by Chiffon's willingness to risk her life for the Straw Hats. Bege later assisted Pudding's plan by delivering a second wedding cake made by Chiffon, Pudding, Sanji, and the WCI 31 to calm Big Mom's rampage. After being convinced by Sanji's cooking, Bege forfeited his desire to poison or booby-trap the cake. When the group reunited with the crew on the Sunny, Sanji went back to his crew while the Fire Tanks took the cake and lured Big Mom and part of her crew away from chasing the Straw Hats, fulfilling Chiffon's debt.

Individuals
Among the following, there are more notable people:
 * Vivi and Carue, as they traveled with the crew for almost the entire Alabasta Saga, and even considered permanently joining them but due to her promise it seems that she is always welcome back.
 * Trafalgar D. Water Law, who initially formed an alliance with Luffy on the pretense to take down the Yonko Kaido, but his true goal was to take down Donquixote Doflamingo. After Doflamingo's defeat, Law later joined the Ninja-Pirate-Mink-Samurai Alliance to defeat Kaido. Law has traveled with the Straw Hats since they left Punk Hazard.

Organizations
Among the following, there are more notable Organizations:
 * The Whitebeard Pirates and their allies, who despite only allying themselves with Monkey D. Luffy in Marineford due to the order of the captain, continued to protect him saying that they will fulfill their father's final order.
 * The Heart Pirates who formed the first pirate alliance with the Straw Hats.
 * The Kozuki Family and Mink Tribe who later join them to form the Ninja-Pirate-Mink-Samurai Alliance.
 * The Straw Hat Grand Fleet who increase the Straw Hats' power and reputation in the New World.