Islamic banking refers to a system of banking or banking activity that is consistent with Islamic law (Shariah) principles and guided by Islamic economics. In particular, Islamic law prohibits usury, the collection and payment of interest, also commonly called riba in Islamic discourse. In addition, Islamic law prohibits investing in businesses that are considered unlawful, or haraam (such as businesses that sell alcohol or pork, or businesses that produce media such as gossip columns or pornography, which are contrary to Islamic values). In the late 20th century, a number of Islamic banks were created, to cater to this particular banking market.

Principles
Islamic banking has the same purpose as conventional banking except that it operates in accordance with the rules of Shariah, known as Fiqh al-Muamalat (Islamic rules on transactions). The basic principle of Islamic banking is the sharing of profit and loss and the prohibition of riba (usury). Amongst the common Islamic concepts used in Islamic banking are profit sharing (Mudharabah), safekeeping (Wadiah), joint venture (Musharakah), cost plus (Murabahah), and leasing (Ijarah).

In an Islamic mortgage transaction, instead of loaning the buyer money to purchase the item, a bank might buy the item itself from the seller, and re-sell it to the buyer at a profit, while allowing the buyer to pay the bank in installments. However, the fact that it is profit cannot be made explicit and therefore there are no additional penalties for late payment. In order to protect itself against default, the bank asks for strict collateral. The goods or land is registered to the name of the buyer from the start of the transaction. This arrangement is called Murabaha. Another approach is Ijara wa Iqtina, which is similar to real-estate leasing. Islamic banks handle loans for vehicles in a similar way (selling the vehicle at a higher-than-market price to the debtor and then retaining ownership of the vehicle until the loan is paid).

There are several other approaches used in business deals. Islamic banks lend their money to companies by issuing floating rate interest loans. The floating rate of interest is pegged to the company's individual rate of return. Thus the bank's profit on the loan is equal to a certain percentage of the company's profits. Once the principal amount of the loan is repaid, the profit-sharing arrangement is concluded. This practice is called Musharaka. Further, Mudaraba is venture capital funding of an entrepreneur who provides labor while financing is provided by the bank so that both profit and risk are shared. Such participatory arrangements between capital and labor reflect the Islamic view that the borrower must not bear all the risk/cost of a failure, resulting in a balanced distribution of income and not allowing lender to monopolize the economy.

And finally, Islamic banking is restricted to Islamically acceptable deals, which exclude those involving alcohol, pork, gambling, etc. Thus ethical investing is the only acceptable form of investment, and moral purchasing is encouraged. Islamic banking is an example of full-reserve banking, with banks achieving a 100% reserve ratio. However, in practice, this is not always the case.

Islamic banks have grown recently in the Muslim world but are a very small share of the global banking system. Micro-lending institutions founded by Muslims, notably Grameen Bank, use conventional lending practices and are popular in some Muslim nations, especially Bangladesh, but some do not consider them true Islamic banking. However, Muhammad Yunus, the founder of Grameen Bank and microfinance banking, and other supporters of microfinance, argue that the lack of collateral or excessive interest in micro-lending is consistent with the Islamic prohibition of usury (riba).

Shariah Advisory Council/Consultant
Islamic banks and banking institutions that offer Islamic banking products and services (IBS banks) are required to establish Shariah advisory committees/consultants to advise them and to ensure that the operations and activities of the bank comply with Shariah principles.

In Malaysia, the National Shariah Advisory Council, which additionally set up at Bank Negara Malaysia (BNM), advises BNM on the Shariah aspects of the operations of these institutions and on their products and services.