No: it's the words whose meaning they supply that are pronouns, not the antecedents. In most cases, antecedents are nouns, but they can sometimes be pronouns, phrases, clauses or even whole sentences. Pronoun is a word category, whereas antecedent is a constituent whose meaning dictates the meaning of a pronoun or other such expression. Here are some examples; the antecedents are in bold and the words whose meaning they supply are underlined :
(1) "These are the bookswhich I bought yesterday".
(2) "The filmthat I needed is not available".
(3) "The daywhen I got married".
(4) "It was themwho committed the robbery".
In (1)-(3), the antecedents are the nouns books, film, and day, and in (4) it is the pronoun them which in turn gets its meaning from another antecedent mentioned in a previous sentence.
(5) "Liz said that she was not available".
(6) "The victim's daughter didn't come to the meeting because she was ill".
In (5) the antecedent is the proper noun Liz, and in (6) the antecedent is the whole noun phrase The victim's daughter
(7) "Max arrived late, which caused us some delay".
(8) "Our rent is due next week". "Which is why we should not spend too much money now".
In (7) the antecedent is a clause, and in (8) the antecedent is a whole sentence!