ὑποθήκη: hypothēkē), sometimes tacit hypothec, is a term used in civil law systems (e.g. the law of most of Continental Europe) or to refer to a registered real security of a creditor over real estate, but under some jurisdictions it may additionally cover ships only (ship hypothec), as opposed to other collaterals, including corporeal movables other than ships, securities or intangible assets such intellectual property rights, covered by a different type of right (pledge).

[1] Originating in Roman law, a hypotheca was essentially a non-possessory pledge over a person's entire estate, but during the Renaissance the device was revived by civil law legal systems as a hypothecatory security interest taken strictly over immovable property and, like the late medieval obligatio bonorum, running with the land (Latin jus persequendi, French droit de suite, Dutch zaaksgevolg, German Folgerecht).

If the debtor cannot pay, the creditor possesses the collateral and therefore can claim its ownership, sell it and thus compensate the lacking cash inflows.

Because hypothecation makes it easier to get the debt and potentially decreases its price; the debtor wants to hypothecate as much debt as possible – but the isolation of 'good assets' for the collateral reduces the quality of the rest of the debtor's balance sheet and thus its credit worthiness.

The detailed practice and rules regulatory hypothecation vary depending on context and on the jurisdiction where it takes place.

Hypothecation is a common feature of consumer contracts involving mortgages – the debtor legally owns the house, but until the mortgage is paid off, the creditor has the right to take ownership (and possibly also possession) – but only if the debtor fails to keep up with repayments.

[4] Under a handful of mixed legal systems, the hypothec was imported as a non-possessory real security over movable property (in opposition to the common-law chattel mortgage).

Of the latter the most important is the landlord's hypothec for rent (corresponding to distress in the law of England), which extends over the produce of the land and the cattle and sheep fed on it, and over stock and horses used in husbandry.

In the US, the legal right for the creditor to take ownership of the collateral if the debtor defaults is classified as a lien.

Term repurchase agreements, less commonly used, extend for a fixed period of time that may be as long as three months.

The Scottish Executive felt that such a mechanism had no part to play in a modern enforcement system, not least because a landlord is able to use other diligences to recover unpaid rent, such as attachment sequestration for rent can now be used to sell only goods that are secured by a right known as the landlord's hypothec, which arises automatically whenever there is a qualifying lease.

The act also states that, notwithstanding the abolition of sequestration for rent, landlord's hypothec does continue as a right in security (section 208(2)(a)).

In Quebec law, the word is nevertheless used in translations as an equivalent of hypothèque, which has a much broader meaning and encompasses the common law equivalents of, inter alia, mortgages, non-possessory liens over movables or immovables, and legal or equitable charges.

2660 of the Quebec Civil Code defines hypothec, providing as follows: The Quebec hypothèque, essentially equivalent to an American non-possessory lien or English legal charge, is an elastic, hypothecatory security interest that has all the rights of recourse (jus exigendi) of an American lien-theory mortgage or English mortgage by way of legal charge, may also be taken over movable and/or immovable property alike, and must be perfected (i.e. registered).

When attaching to movable property, this security interest most closely matches the hypothec as defined at the head of this article.