Can a Muslim woman travel without a mahram?

It depends on the scholar and the situation. The hadith say a woman shouldn't travel without a mahram (her husband or a close male relative she can never marry). Classical schools disagree on how strict that is, and many contemporary scholars allow travel without one when the journey and company are safe. If you're a convert without Muslim male relatives, you're not stuck.

What the hadith say

The Prophet ﷺ said it isn't permissible for a woman who believes in Allah and the Last Day to travel for one day and night except with a mahram (Sahih al-Bukhari 1088). In another narration, a man said his wife was setting out for Hajj while he had signed up for an expedition, and the Prophet ﷺ told him to go with her to Hajj (Sahih al-Bukhari 1862). The aim was clearly to protect women on journeys that, at the time, could be long and dangerous.

How the schools read it

Hanafi: a mahram or husband is required for a journey of travel distance (about three days by classical measure); shorter trips are fine.
Hanbali: a mahram is required for travel, including Hajj; without one, Hajj isn't yet obligatory on her.
Maliki and Shafi'i: for the obligatory Hajj, a woman may travel with a trustworthy, safe group, such as other reliable women, in place of a mahram.

So even classically, the rule wasn't one single position.

Contemporary views

Many scholars today see safety as the reason behind the rule. They point to another hadith where the Prophet ﷺ foretold that a woman would one day travel alone from al-Hira to Mecca to make tawaf, "fearing none but Allah" (Sahih al-Bukhari 3595). On that basis, they allow a woman to travel without a mahram for a real need, like study, work, family or a pilgrimage, when the route, transport and accommodation are safe, often in trusted company. Other scholars keep the requirement and allow exceptions only for genuine necessity. Both views are held by serious scholars. See Can I study abroad as a Muslim?

Hajj and Umrah

Saudi Arabia has relaxed its rules in recent years and now lets women perform Hajj and Umrah without a mahram in many cases, usually as part of an approved group. These rules change, so check the current requirements on official Saudi channels or with a licensed tour operator before you book. Keep in mind that a visa rule tells you what's legally allowed; for the religious side, follow the scholarly view you trust. See Do I have to go to Hajj if I can't afford it?

If you're a convert without Muslim male relatives

Many scholars count a trustworthy non-Muslim father, brother, son or uncle as a mahram, because mahram status comes from family ties, not religion; some, especially in the Hanbali school, don't. If you have no mahram at all, the views above that allow safe, accompanied travel apply to you, and even the stricter views make room for genuine necessity. Talk to an imam you trust about your situation. See Do I need a wali to get married as a Muslim convert woman?

Key points

The hadith on traveling with a mahram are authentic and aim at a woman's safety.
Hanafi and Hanbali scholars are stricter; Maliki and Shafi'i allow a safe group for Hajj.
Many contemporary scholars allow safe travel for a real need.
Check current Saudi rules before booking Hajj or Umrah.

Tip: If you travel without a mahram, choose safe options on purpose: direct flights, well-reviewed accommodation, travel with friends or a group, and share your itinerary with someone back home.