The Wikipedia:Article titles § Disambiguation policy states (in part):

When a topic's preferred title can also refer to other topics covered in Wikipedia, if the article is about the primary topic to which the ambiguous name refers, then that name can be its title without modification, provided it follows all other applicable policies.

The Wikipedia:Disambiguation § Redirecting to a primary topic guideline regarding redirects to primary topics states:

The title of the primary topic article may be different from the ambiguous term [and] ...a disambiguated article title, such as Apostrophe (punctuation), may be moved to its base name (unqualified title) based on a consensus that this is the primary topic for the unqualified term.

When read together, these policies and guidelines indicate that a page for a base name should not be a redirect to a page with the base name plus a parenthetical disambiguator. A valid primary redirect requires the redirect target have a different base name than the redirect. In other words, it is inconsistent with policy and guidelines to have things both ways: have a disambiguated article title with the apparent goal of decreasing ambiguity and confusion, while also directing everyone using the (supposedly) ambiguous undisambiguated title to the disambiguated one via a redirect. Generally in such cases hatnotes should be used to address ambiguity and astonishment, not parenthetical qualifiers added into the title. Unnecessary use of parenthetical disambiguation violates the concision and precision criteria for article titles.

This corollary of article title policy and the disambiguation guideline is the broader case of malplaced disambiguation pages, which states that a base name should not be a redirect to a disambiguation page with the (disambiguation) qualifier, because doing so implies there is no primary topic, and that the disambiguation page should instead exist at (i.e., be moved to) the base name. Likewise, in cases where the base name redirects to an article with a qualified (i.e., disambiguated) title, it implies the article with the qualified title is the primary topic, and the primary topic article should exist at the base name. If instead there is explicit consensus that the article in question should have a qualified title, it implies a lack of a primary topic and that the base name should host a disambiguation page, or redirect to one.

It is nevertheless possible that a base name be a primary redirect to a page with a parenthetical disambiguator, if the base names are different. For example, The Eagles is a primary redirect to Eagles (band); the band is the primary topic for The Eagles but not for Eagles, which is the preferred article title considering Wikipedia:Naming conventions (definite or indefinite article at beginning of name).

As of October 12, 2023, there are a total of 14,000 instances where a base page redirects to itself plus a parenthetical disambiguator.

The same principles apply to cases of partial disambiguation. For example, the Michael Jackson album Thriller is deemed the primary topic among albums with that base name (but not the primary topic for the base name Thriller overall) and thus the article about that album exists at Thriller (album). It would be incorrect for the article to exist at Thriller (Michael Jackson album) and have Thriller (album) redirect there.^[a]

The situation is more complicated in cases of comma-separated disambiguation, which usually involve titles for places. Some region-specific guidance calls for inclusion of a higher-level administrative division in the article title after a comma, even if not required for disambiguation. For example, per WP:USPLACE, most articles on populated places in the United States are titled "Placename, State" even if the place described in the article is the primary topic for "Placename" (or the only topic). In these cases, it is proper for "Placename" to redirect to the article if it is the primary (or only) topic for the base name, e.g. Nashville redirects to the article about the city at Nashville, Tennessee. In cases where there is no specific naming convention that indicates that comma-separated disambiguators should be included when disambiguation is not required, then generally the article should exist at the base name if it is the primary (or only) topic, as described above in cases involving parenthetical disambiguators, but this may be best determined on a case-by-case basis via discussion.

Some topic-specific naming conventions expressly call for the use of parenthetical disambiguators even when the base name is not ambiguous, forming exceptions to normal article title policy by consensus. Examples include:

• Leeds North West is precise enough to be unambiguous, but Wikipedia:Naming conventions (UK Parliament constituencies) specify the addition of the qualifier in Leeds North West (UK Parliament constituency) with a redirect from Leeds North West.
• M-185 is precise enough to be unambiguous, but Wikipedia:Naming conventions (U.S. state and territory highways) specify adding the qualifier M-185 (Michigan highway) with a redirect from M-185.

As with otherwise unnecessary comma-separated disambiguators, base names should in these cases redirect to the disambiguated page (if it is the only or primary topic).

This issue commonly arises when a base name is deemed to be potentially ambiguous with similarly written base names, thus the article at the base name is moved to one with parenthetical disambiguation, but the resulting redirect is left in place to still bring users to that article as the primary topic. However, such a move is contrary to the Wikipedia:Article titles § When a spelling variant indicates a distinct topic policy. In such a case, other disambiguation techniques, particularly hatnotes, are used to distinguish similar names that may be confused with one another, and parenthetical disambiguation is inappropriate because the article is the primary topic. Adding a parenthetical disambiguator does not make the situation any less astonishing, because any user seeking a different, similarly spelled topic will still be disappointed to have reached the incorrect page, and still must make use of hatnotes to quickly direct them to the page sought.

Sometimes pages may be moved to titles that include parenthetical disambiguation due to the title being ambiguous with another topic, but the resulting redirect (the page at the base name) is left to redirect there. Such a move does not provide disambiguation, because everyone searching the ambiguous topic will be brought to the qualified title. In cases where the other topic is covered on Wikipedia, a disambiguation page may be created over the redirect at the base name, unless one of the topics is the primary topic (see below). In contrast, when the other topic is not covered in Wikipedia, there is nothing to disambiguate and nowhere else for the page at the base name to go, and therefore moving the article at the base name to one with parenthetical disambiguation is contrary to Wikipedia:Article titles § Disambiguation policy, which indicates that only titles covered in Wikipedia should be disambiguated. In such situations, the article should exist at the base name.

It is also possible for this situation to arise when attempting to establish a primary topic when there previously was not one: a user could move the disambiguation page currently at the base name out of the way to the version of the page with the (disambiguation) qualifier, then, realizing they are unable to move the primary topic article over the resulting redirect, choose to simply retarget the redirect to the primary topic article. In such a case, if you agree with the establishment of the primary topic, submit a technical request to move the primary topic article to the base name; if you disagree or are unsure, revert the move of the disambiguation page and optionally initiate a requested move discussion, making sure to explicitly request moves for both the disambiguation page and primary topic article.

When encountering such a situation, if you are sure the article is the only topic for that exact spelling of the base name, or is the primary topic for it, consider one of the following:

• Boldly move the article (back) to the base name, especially if part of a bold-revert-discuss cycle where you are reverting another user's undiscussed bold move.
• Submit a technical move request if you cannot complete the move yourself under those circumstances.
• Initiate a requested move discussion if there is history of discussion, page moves, or other edits related to the issue that would indicate the article title is potentially controversial and consensus should be established via discussion.

If there is consensus that the article be at a disambiguated title, and/or you believe the article is not the primary topic, the base name should likely host the relevant disambiguation page, or redirect to it. In this case, it may be appropriate to submit a technical request to move the disambiguation page (likely currently with a (disambiguation) qualifier) to the base name, or start a requested move discussion if potentially controversial or consensus is unclear.

If you are unsure whether the article in question is the primary topic for the base name, nominate the base name page (currently a redirect) at redirects for discussion to discuss how to handle the inappropriate status quo. Such a discussion could result in confirming the current redirect target is indeed the primary topic (or only topic) for the base name and moving the article over the redirect as a matter of course, moving a different article to the base name as the primary topic, forming a disambiguation page over the redirect at the base name (if it is actually ambiguous but there is no primary topic), retargeting the redirect to an existing disambiguation page, retargeting the redirect to a different article (with a different base name) as a primary redirect, or additional discussion at another venue.