A Scottish statutory instrument (SSI; Scottish Gaelic: Ionnsramaid Reachdail na h-Alba) is subordinate legislation made by the Scottish Ministers, as well as subordinate legislation made by public bodies using powers provided to be exercisable by Scottish statutory instrument. SSIs are the main form of subordinate legislation in Scotland, being used by default to exercise powers delegated to the Scottish Ministers, the Lord Advocate, the High Court of Justiciary, the Court of Session, and the King-in-Council.

The Interpretation and Legislative Reform (Scotland) Act 2010 defines what a Scottish statutory instrument is. Before this Act, SSIs were governed by the Statutory Instruments Act 1946, which continues to govern UK statutory instruments.

SSIs, and the power to enable the creation of subordinate legislation in general, are not mentioned in the original text of the Scotland Act 1998, which devolved powers to the Scottish Parliament. Rather, this power is implied by the statement that Acts of the Scottish Parliament are law to the extent that they are not "outside the legislative competence of the Parliament," without any subsequent reservation of the power to make subordinate legislation.

Before Scottish devolution, subordinate legislation applying only to Scotland was published as a subseries of the larger UK statutory instrument (SI) series. This subseries is now used for SIs which deal with reserved matters in relation to Scotland.

An SSI is made, with some exceptions, by a body exercising executive governmental functions – that is, a body responsible for putting the law into effect ("executing" the law) rather than a body responsible for defining the law (the legislature) or a body responsible for interpreting the law (the judicature). As a result, an SSI will provide specific details on how an Act should be put into effect and may amend existing Acts or SSIs to reflect that the law has changed. In other cases, an SSI may repeal parts of the law which had before been impliedly repealed.

For example, section 15 of the Charities and Trustee Investment (Scotland) Act 2005 allows the Scottish Ministers to make regulations setting out how charities refer to themselves in documents, and the Charities References in Documents (Scotland) Regulations 2007 sets out in regulation 2 how a charity must refer to itself, and in regulation 4 on which documents a charity must make such references.

In other cases, an SSI may be used to bring into force parts of the law through so-called "commencement orders." In these cases, sections of Acts may have no legal force until brought into force, which may allow time for accommodating preparations to be made. One example of a commencement order is the Bankruptcy (Scotland) Act 2016 (Commencement) Regulations 2016, which brought almost the entirety of the Bankruptcy (Scotland) Act 2016 into force.

Another example, although not involving SSIs, is the Health and Safety at Work etc. Act 1974, which applies to Scotland and makes provisions relating to ensuring safety in the workplace. This Act covers a wide remit, and so UK SIs have been issued under the same sections to cover different industries. Specifically, some sections of this Act which allow making SIs were used to make both the Control of Substances Hazardous to Health Regulations 2002 and the Control of Vibration at Work Regulations 2005 even though those regulations are not related.