The information in this Preliminary Prospectus is not complete and may be changed. We
may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This Preliminary Prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these
securities in any jurisdiction where the offer or sale is not permitted.
SUBJECT TO COMPLETION DATED July 22, 2026
PRELIMINARY BASE PROSPECTUS
$[ ]
Franklin Municipal Opportunities Trust
Common Shares
Subscription Rights to Purchase Common Shares
The Fund. Franklin Municipal Opportunities Trust, a Massachusetts business trust (the “Fund”), is a diversified, closed-end management investment company.
Investment Objective. The Fund’s investment
objective is to seek as high a level of current income exempt from federal income tax consistent with preservation of capital. There can be no assurance that the Fund will achieve its investment objective.
Investment Strategies. Under normal market conditions, at least 80% of the Fund’s assets will be invested in municipal bonds.
The Fund’s shares of beneficial interest, without par value (“Common Shares”), are listed on the New York Stock Exchange
(“NYSE”) under the trading or “ticker” symbol “PMO.” The net asset value (“NAV”) of our Common Shares at the close of business on [ ], 2026 was $[ ] per share,
and the last sale price per share of our Common Shares on the NYSE on that date was $[ ].
Offering. The Fund may offer,
from time to time, in one or more offerings, our Common Shares, which we also refer to as our securities, at prices and on terms to be set forth in one or more Prospectus Supplements to this Prospectus.
We may offer and sell our securities to or through underwriters, through dealers or agents that we designate from time to time, directly to
purchasers, through at-the-market offerings or through a combination of these methods. See “Plan of Distribution—Distribution Through Agents,”
“—Distribution Through Underwriters” and “—Distribution Through Dealers.”
Leverage. The
Fund currently uses leverage through the issuance of Preferred Shares and may in the future continue to use leverage through the issuance of Preferred Shares, subject to the requirements of the 1940 Act and the Fund’s Amended and Restated
Bylaws (the “Bylaws”). As of April 30, 2026, the Fund’s Remarketed Preferred Shares represented 44.5% of net assets applicable to Common Shares. See “Leverage,” “Description of Shares—Preferred
Shares” and “Risks—Risks Related to the Fund—Leverage Risk.”
This Prospectus provides you with a general
description of the securities that we may offer. Each time we use this Prospectus to offer securities, we will provide a Prospectus Supplement that will contain specific information about the terms of that offering. The Prospectus Supplement may
also add, update or change information contained in this Prospectus. This Prospectus, together with any Prospectus Supplement, sets forth concisely the information about us that a prospective investor ought to know before investing. You should read
this Prospectus and the related Prospectus Supplement before deciding whether to invest and retain them for future reference. A Statement of Additional Information, dated , 2026 (the “SAI”), containing
additional information about us, has been filed with the Securities and Exchange Commission (“SEC”) and is incorporated by reference in its entirety into this Prospectus. You may request a free copy of the SAI (the table of contents of
which is on page i of this Prospectus), annual and semi-annual reports to shareholders (when available), and additional information about the Fund by calling (800)342-5236, by writing to the Fund at 100
Federal Street, Boston, Massachusetts 02110 or visiting the Fund’s website (http://www.franklintempleton.com/investments/options/closed-end-funds).
Shares of closed-end investment companies frequently trade at discounts to their NAVs. If our Common
Shares trade at a discount to our NAV, the risk of loss may increase for purchasers of our Common Shares, especially for those investors who expect to sell their Common Shares in a relatively short period after purchasing shares in this offering.
See “Risks—Market Price Discount from Net Asset Value Risk.”
Investing in the Fund’s securities involves
certain risks including risks that make the offering of securities speculative (See “Risks—Below Investment Grade (High-Yield or Junk Bond) Securities Risk”). You could lose some or all of your investment. See “Risks” beginning on page 34 of this Prospectus and any Prospectus Supplement.
Neither the SEC nor any state securities
commission has approved or disapproved of these securities or determined if this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.
The Fund’s securities do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured
depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other governmental agency.