Oracle adapters for Ruby ORMs allow Ruby applications to connect to and interact with Oracle databases. The main adapters discussed are: 1) ActiveRecord OracleEnhanced adapter which provides full ActiveRecord compatibility and addresses Oracle-specific issues and limitations. 2) DataMapper Oracle adapter which provides an alternative ORM framework that supports Oracle and other databases. 3) Low-level OCI8 and ruby-oci8 gems for direct SQL and PL/SQL access from Ruby applications.