In modern usage, hijab (Arabic: حجاب, romanized: ḥijāb, pronounced [ħɪˈdʒaːb]) generally refers to headcoverings worn by some Muslim women. It is similar to the wimple, apostolnik, and mantilla worn by some Christian women. While a hijab can come in many forms, it often specifically refers to a headscarf, wrapped around the head and neck, covering the hair, neck, and ears but leaving the face visible. The use of the hijab has been on the rise worldwide since the 1970s and is viewed by many Muslims as expressing modesty and faith. However, some Muslims maintain that the practice of covering the hair with a hijab is not mandated in Islam.

The term ḥijāb was originally used to denote a partition, a curtain, or was sometimes used for the Islamic rules of modesty. This is the usage in the verses of the Qur'an, in which the term sometimes refers to a curtain separating visitors to Muhammad's main house from his wives' residential lodgings. This has led some to claim that the mandate of the Qur'an applied only to the wives of Muhammad, and not to the entirety of women. Another interpretation can also refer to the seclusion of women from men in the public sphere, whereas a metaphysical dimension may refer to "the veil which separates man, or the world, from God". For some, the term for headscarf in the Qur'an is khimār (Arabic: خِمار).

According to the understanding of the "oldest legal systems", only the wives of Muhammad were those who were instructed to hijab with the verse (33:59), and none of them had a condition for women to cover. Despite this, all orthodox sharia schools ordered that parts of the body, especially the neck, ankles, and under the elbows, be covered in public. There is no consensus among those who consider the subject as a necessity, such as how much of the veil is a necessity. Some legal systems accept the hijab as an order to cover everything except the face and hands while others accept it as an order that covers the whole body, including the face and hands. These guidelines are found in texts of hadith and fiqh developed after the revelation of the Qur'an. Some believe these are derived from the verses (ayahs) referencing hijab in the Qur'an; others believe that the Qur'an does not mandate that women need to wear a hijab. Some religious groups consider the issue of veiling in Islam only as a recommendation made according to the conditions of the past, and they believe that giving it as a necessity is an imposition of an Islamist ideology. The Muslim Reform Movement emphasized that the jilbāb and khimar mentioned in the Qur'an are pre-Islamic clothing, they were not brought by the Qur'an, the hijab of the Qur'an never means a headscarf, and the Qur'an only advises on how to wear them.

The hijab is currently required by law to be worn by women in Iran, Afghanistan and the Indonesian province of Aceh. It is no longer required by law in Saudi Arabia since 2018, although Crown Prince Mohammad bin Salman has stated that women, similar to other Gulf countries, must still wear "decent and respectful attire". In Gaza, Palestinian jihadists belonging to the Unified Leadership (UNLU) have rejected a hijab policy for women. They have also targeted those who seek to impose the hijab. Other countries, both in Europe and in the Muslim world, have passed laws banning some or all types of hijab in public or in certain types of locales. Women in different parts of the world have also experienced unofficial pressure to wear or not wear a hijab. The Muslim Reform Movement holds that hijab of the Qur'an simply meant "barrier" and that it was used in the context of both men and women; the jilbab and the khimar were pre-Islamic clothes and the Qur'an simply recommended how to wear these, rather than imposing a new clothing requirement.