Is Sylvia Plath's poem "Daddy" an autobiographical poem?
Many critics think so, yes. There are definitely parts of the poem that parallel her feelings about her father and about a male-dominated society. Plath felt oppressed by this society and was expressed in her poetry. There are very few poets whose poems are so very connected to the their lives...Plath is one of these poets. Her poems are intensely personal and much is revealed about her life through her poetry:
She saw herself as a product of a male society, molded by males to suit their particular whims or needs. Her contact with females in this context led inevitably to conflict and competition. This duality in her self was never overcome, never expelled, or, worse, never understood. Having failed to manipulate her manipulators, she tried to find identity by destroying her creators. Set free from the basis she had always known even if she despised it, she had nowhere else to go but to the destruction of the self as well. (Enotes)
Plath's poems are often seen as being confessional and "Daddy" is commonly viewed as being merely an autobiographical attack on her enigmatic and difficult relationship with her father, Otto Plath ( with a dig a Ted Hughes thrown in for good measure). This view is an underdeveloped one, however.
In terms of style we can see elements of her influence from Anne Sexton and Robert Lowell surfacing here but the key difference is that Plath created numerous personae in her works. This sets it apart from the Confessionals and it is from this that a deeper reading becomes apparent. In "Daddy" Plath cites the I-voice as being "a girl with an electra complex" and in doing so unleashes a more complicated Psychological element to the poem, which becomes clearly Freudian in places.
In short, the answer is yes and no. She does, evidently, use autobiographical detail within the piece but to say it is wholly this is a limited assertion. The best way to analyse her work is by considering different readings of her verse - Autobiographical, Pyschological, Mythological...and to question what issues/themes these ultimately reveal.