See Chapter 7 Trustee, Chapter 11 Trustee, and United States Trustee.
In Chapter 11 cases where the debtor remains in possession and control of its property, the debtor (with minor exceptions) has the rights, powers, and functions of a trustee appointed under the Code. The Code often references only the rights and functions of “the trustee,” but in Chapter 11 cases those references should be read to say “the trustee or debtor in possession.”
Bankruptcy Code § 1107. See also Debtor in Possession.