The Maiamais are a race from The Legend of Zelda: A Link Between Worlds. They are small marine creatures somewhat similar to hermit crabs, though it is implied they may also someday grow to resemble octopi (or Octoroks) judging by Mother Maiamai's appearance.
The Maiamais are part of a side quest wherein Link must find 100 of Mother Maiamai's lost children that have been spread throughout Hyrule and Lorule, with each world containing 50 Lost Maiamais in all. They will not appear before Link has met with Mother Maiamai for the first time, however. When the side quest is begun, Mother Maiamai allows Link to use the Maiamai Map to find out how many Maiamais are left to be found in any specific region of the current world. For every group of ten Maiamais returned, Mother Maiamai will upgrade one of Link's items (provided it is not a rental) into a "Nice" version, with a different design and enhanced features. If all 100 Maiamais are obtained Link can learn the Great Spin Attack from Mother Maiamai.
After Link has returned all the Lost Maiamais to Mother Maiamai, they return to their own dimension with the exception of a single Lost Maimai who decides to stay behind.
As part of the A Link Between Worlds DLC, Maiamais appear as Item Cards on the Lorule Adventure Map which can be given to Mother Maiamai on certain squares to obtain treasure. There is also a Fairy Clothing option called the Shell Aura based on the Maiamai.