Which part of speech is the word 'who' in the following sentence?
"God helps those who help themselves."

The pronoun 'who' is a relative pronoun.
The function of a relative pronoun is to link a subordinate clause to the main clause.
In the given sentence, the main clause "God helps those" is linked to the subordinate clause "help themselves" by the pronoun 'who'.
Hence, the option "Relative pronoun" is correct.