This morning (the morning of today). The colloquial reading is けさ.
今朝は早く起きた。
I woke up early this morning.
今朝のニュースで事故を知った。
I learned about the accident on this morning's news.
今朝、雨が降っていたから傘を持って行った。
It was raining this morning, so I took an umbrella.