What is shirk and how do I avoid it?

Shirk is giving any part of Allah's exclusive rights, such as worship, ultimate power or complete trust, to someone or something else. It is the one sin Allah does not forgive if a person dies upon it, but it is forgiven when a person repents sincerely before death. Shirk can be major, which takes you out of Islam, or minor, such as showing off in worship.

What shirk means

Shirk means "association": making someone or something a partner with Allah. The Quran treats it as the gravest wrong:

وَإِذْ قَالَ لُقْمَـٰنُ لِٱبْنِهِۦ وَهُوَ يَعِظُهُۥ يَـٰبُنَىَّ لَا تُشْرِكْ بِٱللَّهِ ۖ إِنَّ ٱلشِّرْكَ لَظُلْمٌ عَظِيمٌ "O my dear son! Never associate anything with Allah in worship, for associating others with Him is truly the worst of all wrongs." Quran 31:13

The Prophet ﷺ listed joining partners with Allah as the biggest of the great sins (Sahih al-Bukhari 5976). Allah does not forgive a person who dies upon shirk, but He forgives everything less than that for whoever He wills (Quran 4:48). The good news is that anyone who sincerely turns back to Allah before death, even from shirk, is forgiven.

Major shirk

This is directly worshipping, praying to or asking for help from anyone other than Allah, or believing someone else shares His power. Examples:

Praying to saints, idols, spirits or the dead as if they can answer.
Believing a person, object or star controls your fate on its own.
Claiming that Allah has a son, partner or equal.

The short surah Al-Ikhlas sums up the belief in one God: "Say, He is Allah, One... there is none comparable to Him" (Quran 112:1-4). See What is tawhid in Islam?

Minor shirk

This does not take a person out of Islam, but it harms faith and must be avoided. The Prophet ﷺ warned of "hidden polytheism": a man who stands to pray and makes his prayer look good because someone is watching (Sunan Ibn Majah 4204). This is showing off, called riya. Another example is swearing by something other than Allah. The Prophet ﷺ said that whoever does so has committed disbelief or shirk (Jami at-Tirmidhi 1535).

Everyday things to watch for

Horoscopes and fortune-telling: believing they reveal the unseen or control your day. See Can I still read my horoscope after becoming Muslim?
Amulets and lucky charms: trusting them to protect you on their own. The Prophet ﷺ called spells, charms and love-potions of this kind shirk (Sunan Abi Dawud 3883). See Can I wear an evil eye bracelet as a Muslim?
Showing off: praying or giving charity mainly to be praised.
Relying only on people or money: forgetting that everything happens by Allah's permission.

How to avoid it

Learn the meaning of "La ilaha illa Allah" (There is no god but Allah).
Ask Allah directly in dua, with no go-between.
Renew your intention often, so deeds are done for Allah.
Take medicine, work and plan, but trust that Allah decides the result.
If you slip, repent quickly. Allah is Most Forgiving.

Key points

Shirk means giving others what belongs only to Allah.
Major shirk leaves Islam; minor shirk includes showing off.
Allah forgives a person who repents from shirk before death.
Avoid charms, fortune-telling and worship done to impress people.

Tip: If you are unsure whether something crosses the line, ask a trusted imam. Most worries come from habits picked up before Islam, not from bad intention.