Consider Henrik Ibsen as a realist, as a naturalist & as a symbolist.

Ibsen is considered the Father of Modern Drama.  He is
considered the first modern realist because he dealt with contemporary issues, I.e. he
explores the role of women in modern society in The Doll's House. 
Nora could be considered the first feminist when she declares her freedom at the end of
the play.

As for naturalist, I'm not sure what you mean by
this.  Admittedly realism and naturalism are closely related but naturalism is
considered more gritty, I.e. The Lower
Depths.

Although he may use some symbols, as do
many writers, I would not consider him a symbolist.   I see more symbolism in
The Glass Menagerie.

By defying
accepted practices in the theatre and writing about real issues confronting recognizable
people, he opened the door to modern drama, thus the title Father of Modern Drama when
referring to Ibsen.