Tomodachi Collection is a 2009 social simulation video game developed and published by Nintendo for the Nintendo DS. It follows the daily interactions between interactive Miis, customizable avatars, who reside on an island overseen by the player, as they build relationships and solve problems.

Junior Nintendo employees began developing the game in October 2005, replicating the Nintendo-published video game Tottoko Hamtaro: Tomodachi Daisakusen Dechu (2000). Titled Otona no Onna no Uranai Techō, the prototype featured character-creation avatars that served as the progenitors for what would become the Miis. With suggestions from Nintendo president Satoru Iwata and game designer Shigeru Miyamoto, the team was reassigned to implement the Miis onto the Wii console, during which the game's production was put on hold. Following the Wii's release in December 2006, the project restarted as Tomodachi Collection around April 2007. Developers sought to create entertaining gameplay that emphasized the human-like characteristics of the Miis, whom players were incentivized to create in the image of their real-world friends and family.

Tomodachi Collection was released solely in Japan on June 18, 2009. It received contemporary and retrospective praise for its unconventional tone and presentation. Tomodachi Collection was a domestic commercial success, selling 3.2 million copies by March 31, 2010, making it one of the best-selling DS games.

Plans to localize the title overseas never came to fruition, largely because the Miis' voice synthesis program was unable to replicate English. It spawned the Tomodachi Life series beginning with a direct sequel, Tomodachi Life, that was released in Japan in 2013 for the Nintendo 3DS and internationally the following year. Another sequel, Tomodachi Life: Living the Dream, released on the Nintendo Switch worldwide on April 16, 2026.

Tomodachi Collection is a social simulation game featuring Miis, user-customizable avatars, who populate an apartment complex on an island. To add Miis, the player can transfer existing Miis directly from their Wii to their Nintendo DS, import Miis from other players' DS consoles via wireless local connectivity, or create new ones from scratch using the in-game Mii Maker. In any case, the player manually modifies their Miis' appearance and personality. There are four temperament categories Miis can occupy, which, together with their assigned date of birth, determine an "ideal job" that matches them. The Miis audibly speak through computer-generated voice synthesis. A maximum of 100 Miis can live on the island at once.

After creation, Miis request assistance with particular problems, signified by the presence of a thought bubble. These issues include asking for food, clothing, guidance on prospective relationships, and player participation in short minigames. Satisfying their needs advances their level, a numeric progression system, upon which the player can gift them new clothes, interior designs for their apartment, personalized catchphrases, or songs for them to perform. Completing minigames awards the player with valuables that can be exchanged for in-game currency. The player can optionally eavesdrop on the Miis' dreams while they sleep.

Tomodachi Collection has no end condition; the player's only goal is to maintain their Miis' satisfaction and passively observe their actions. Outside of the player's direct influence, the Miis regularly interact with one another, forming friendships and occasionally experiencing conflict. If two friendly Miis are romantically attracted to one another, one can confess their love to the other; if the confession is successful, the two are paired as a couple. Marriage can occur following additional interactions. As the player continuously appeases the Miis, new venues and shops on the island become unlocked. These include a Career Hall where jobs are formally assigned to Miis, a Compatibility Tester that gauges two Miis' likelihood of friendship, and a vendor for purchasing apartment interiors. An in-universe news broadcast occurs regularly to inform the player of recent events on the island. Time-sensitive events held by the Miis also take place in the island's fountain. Time on the island passes parallel to that set on the player's console, even when the console is powered off.

Tomodachi Collection was first conceptualized around October 2005 by a small team of junior employees at Nintendo SPD. Its premise was inspired by the fortune-telling video game Tottoko Hamtaro: Tomodachi Daisakusen Dechu (2000), published by Nintendo for the Game Boy Color in Japan. Tottoko Hamtaro, whose core audience was young girls, had users register a list of virtual profiles of close friends to measure compatibility and generate predictions about their day-to-day lives. Producer Yoshio Sakamoto agreed with some female employees' idea for a derivative version of Tottoko Hamtaro geared to older women, the thought of which, he said, "stayed with me"; he would then find himself "in a team made up of all new people and we were relatively free to do what we wanted". With the dual purpose of elevating the Nintendo DS' overall appeal to women, the project became tentatively known as Otona no Onna no Uranai Techō (大人のオンナの占い手帳, lit. 'Women's Fortune Telling Pocket Notebook'). Initially including only textual information about personal names and birthdays, the team resolved to add a three-dimensional character creation mechanism. This system—inspired by the Japanese game fukuwarai, which involves assembling a face using disembodied parts—had players manually combine selected face elements to create caricatures of real-world people. The ability to rotate, resize, and reposition facial features was added, enhancing the character creator's accuracy.