Exhibit 19(b)

CERTIFICATION

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

(Subsections (a) and (b) of Section 1350, Chapter 63 of Title 18, United States Code)

In connection with the annual report of the Nuveen Municipal High Income Opportunity Fund (the “Fund”) on Form N-CSR for the period ended October 31, 2025, as filed with the Securities and Exchange Commission (the “Report”), the undersigned officers of the Fund certify that, to the best of each such officer’s knowledge:

 

1.

The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

 

2.

The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Fund.

 

Date: January 7, 2026				By:		/s/ David J. Lamb
						David J. Lamb
						Chief Administrative Officer (principal executive officer)

 

Date: January 7, 2026				By:		/s/ Marc Cardella
						Marc Cardella
						Vice President and Controller (principal financial officer)