Techniques are disclosed relating to performing database defragmentation operations by autonomously rebuilding index objects stored in one or more tablespaces of a database. In various embodiments, the disclosed techniques include autonomously performing defragmentation operations for one or more tablespaces in a database in an online manner such that a server system may continue to service data access requests while performing the defragmentation operations. In one non-limiting embodiment, for example, the disclosed techniques include selecting a first tablespace to defragment based on its level of fragmentation (e.g., relative to the other tablespaces). The server system may then rebuild index objects, from the first tablespace, to a new tablespace such that the index objects are stored in the new tablespace without fragmentation. The server system may then reclaim at least a portion of the storage space used to store the first tablespace and repeat, as desired, to autonomously defragment multiple tablespaces.