Final answer:
No, a validly baptized non-Catholic does not need to be re-baptized when joining the Catholic Church. RCIA is the process they go through to become fully initiated members of the Church.
Step-by-step explanation:
If a validly baptized non-Catholic wishes to be received into the Catholic Church, they do not need to be re-baptized. This is because the Catholic Church recognizes the validity of baptism performed by other Christian denominations as long as certain criteria are met. According to Catholic canon law, a valid baptism requires the use of water, the invocation of the Trinity (Father, Son, and Holy Spirit), and the intention to baptize in accordance with the Christian faith.
For example, if a person was baptized in a non-Catholic Christian church and meets these criteria, their baptism is considered valid by the Catholic Church. They would not be re-baptized upon joining the Catholic Church, but rather go through a process called RCIA (Rite of Christian Initiation of Adults) which would involve learning about Catholic beliefs and practices, receiving the sacraments of Eucharist and Confirmation, and making a profession of faith.