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In computer science, a B-tree is a tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic amortized time. The B-tree is a generalization of a binary search tree in that a node can have more than two children. (, p. 123) Unlike self-balancing binary search trees, the B-tree is optimized for systems that read and write large blocks of data. It is commonly used in databases and filesystems.

A B*-tree is a tree data structure, a variety of B-tree used in the HFS and Reiser4 file systems, which requires non-root nodes to be at least 2/3 full instead of 1/2. To maintain this, instead of immediately splitting up a node when it gets full, its keys are shared with the node next to it. When both are full, then the two of them are split into three. It also requires the 'leftmost' key never to be used.

In computer science, a B+ tree or B plus tree is a type of tree which represents sorted data in a way that allows for efficient insertion, retrieval and removal of records, each of which is identified by a key. It is a dynamic, multilevel index, with maximum and minimum bounds on the number of keys in each index segment (usually called a "block" or "node"). In a B+ tree, in contrast to a B-tree, all records are stored at the leaf level of the tree; only keys are stored in interior nodes.