The adjective oblivious means not being aware of something or someone. It can also mean forgetfulness.

Synonyms are inattentive, blind, deaf or unconcerned.

The word origins from Latin (mid. 15th century) obliviosus meaning “forgetful, that easily forgets or producing forgetfulness”. 1862 the meaning changed to “unaware, unconscious (of something)”. If the word is used in the sense of forgetfulness, it has to follow by “of”. It can follow either by “of” or “to” when used in the sense of conscious or aware of something or someone.

They were very rude and oblivious to anyone not included in their group.

Tom was oblivious of his surrounding during the speech.

He stumbled into the room oblivious to the condition it was in.