Donald Trump has not banned nor is he currently planning to ban same-sex marriage in the United States.
Trump has banned (or is planning to ban) gay marriage

How Gay Marriage Is Under Threat in the Trump Era - TIME
Source: time.com
Key Evidence
The U.S. Supreme Court ruled same-sex marriage legal in 2015 and it has not been overturned.
politifact.compolitifact.comA Facebook post claims that President-elect Donald Trump has banned same-sex...
Legal experts and LGBTQ advocacy groups confirm that existing marriages are secure and no federal ban exists or is planned.
nclrights.orgnclrights.org2024 Update: Now that Trump Has Been Elected, Can Our Marriage Be Undone?
While some state lawmakers have targeted LGBTQ rights, these efforts do not constitute a federal ban on same-sex marriage.
theconversation.comtheconversation.comSame-sex marriage is under attack by state lawmakers, emboldened by Trump’s...
What the Evidence Shows
The claim that Donald Trump has banned or is planning to ban gay marriage is false. The U.S. Supreme Court legalized same-sex marriage nationwide in 2015 with the Obergefell v. Hodges decision, and this ruling remains in effect as of 2025. While there have been political and social challenges to LGBTQ rights during Trump's presidency, including some state-level legislative efforts emboldened by broader conservative movements, there is no executive order or federal law enacted by Trump that bans same-sex marriage. Furthermore, Trump does not have the unilateral authority to overturn Supreme Court decisions on this matter.
Concerns about LGBTQ rights under Trump's administration often relate to other issues such as transgender healthcare and anti-discrimination protections, but these do not equate to a ban on same-sex marriage. Advocacy groups and legal experts have confirmed that existing marriages remain secure and that the freedom to marry is not currently under direct threat from federal executive action.
In summary:
Same-sex marriage remains legal nationwide.
Trump has not issued any ban or formal plan to ban gay marriage.
Challenges to LGBTQ rights exist but are separate from the legality of same-sex marriage.
The Supreme Court's ruling continues to protect marriage equality.
Therefore, the statement is factually incorrect based on current legal and political realities.