Section Manager, Section Chief
noun, suffix
Remember how 社長 is the company president? This uses the same 長 meaning (where it means something like "boss"). Since 課 means section, this is the section manager.
かちょう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
先月、課長になりました。
I became a section manager last month.
課長になれて、うれしいです。
I'm happy to have become a section chief.
うちの課の課長、少しうざいんだよね。
The section chief in our section is a bit annoying, you know.