SMART is a mnemonic/acronym, giving criteria to guide in the setting of objectives, for example in project management, employee-performance management and personal development. The letters S and M generally mean specific and measurable. Possibly the most common version has the remaining letters referring to achievable, relevant and time-bound. However, the term's inventor had a slightly different version and the letters have meant different things to different authors, as described below. Additional letters have been added by some authors.
The first-known use of the term occurs in the November 1981 issue of Management Review by George T. Doran. The principal advantage of SMART objectives is that they are easier to understand and to know when they have been done. SMART criteria are commonly associated with Peter Drucker's management by objectives concept.
Often the term S.M.A.R.T Goals and S.M.A.R.T Objectives will surface. Although the acronym SMART generally stays the same, objectives and goals can differ. Goals are the distinct purpose that is to be anticipated from the assignment or project.  Objectives on the other hand are the determined steps that will direct full completion of the project goals. 
The November 1981 issue of Management Review contained a paper by George T. Doran called There's a S.M.A.R.T. way to write management's goals and objectives. It discussed the importance of objectives and the difficulty of setting them.
Ideally speaking, each corporate, department, and section objective should be:
- Specific – target a specific area for improvement.
- Measurable – quantify or at least suggest an indicator of progress.
- Assignable – specify who will do it.
- Realistic – state what results can realistically be achieved, given available resources.
- Time-related – specify when the result(s) can be achieved.
Notice that these criteria don't say that all objectives must be quantified on all levels of management. In certain situations it is not realistic to attempt quantification, particularly in staff middle-management positions. Practicing managers and corporations can lose the benefit of a more abstract objective in order to gain quantification. It is the combination of the objective and its action plan that is really important. Therefore serious management should focus on these twins and not just the objective.
Each letter in SMART refers to a different criterion for judging objectives. Different sources use the letters to refer to different things. Typically accepted criteria are as follows.
|S||Specific||(Strategic and specific)|
|A||Achievable||Agreed, attainable, action-oriented, ambitious, aligned with corporate goals, (agreed, attainable and achievable)|
|R||Relevant||Realistic, resourced, reasonable, (realistic and resourced), results-based|
|T||Time-bound||Trackable, time-based, time limited, time/cost limited, timely, time-sensitive, timeframe, testable|
Choosing certain combinations of these labels can cause duplication, such as selecting 'attainable' and 'realistic'. They can also cause significant overlapping as in combining 'appropriate' and 'relevant'. The term 'agreed' is often used in management situations where buy-in from stakeholders is desirable (e.g. appraisal situations.)
When creating a S.M.A.R.T Objective, there is specific criteria one should follow. 
Some authors have added additional letters giving additional criteria. Examples are given below.
- Trackable and agreed
- Realistic and relevance. 'Realistic' refers to something that can be done given the available resources. 'Relevance' to the bigger picture and vision.
- Specific, Measurable, Actionable, Realistic, Testable, Verifiable, and Traceable
- Specific, Measurable, Actionable, Realistic, Time-bound, Why (Motivator)
Other mnemonic acronyms also give criteria to guide in the setting of objectives.
- Positively stated
- Doran, G. T. (1981). "There's a S.M.A.R.T. way to write management's goals and objectives". Management Review. AMA FORUM. 70 (11): 35–36.
- Bogue, Robert. "Use S.M.A.R.T. goals to launch management by objectives plan". TechRepublic. Retrieved 10 February 2018.
- SAMHSA Native Connections. "Setting Goals and Developing Specific, Measurable, Achievable, Relevant, and Time-bound Objectives" (PDF). Substance Abuse and Mental Health Services Administration.
- Why SMART objectives don't work.
- Yemm, Graham (2013). Essential Guide to Leading Your Team : How to Set Goals, Measure Performance and Reward Talent. Pearson Education. pp. 37–39. ISBN 0273772449. Retrieved 2013-07-05.
- Piskurich, George M. (2011). Rapid Instructional Design : Learning ID Fast and Right. John Wiley & Sons. p. 132. ISBN 1118046927. Retrieved 2013-07-05.
- Richman, Larry (2011). Improving Your Project Management Skills. AMACOM Division of American Management Association. p. 65. ISBN 0814417299. Retrieved 2013-07-11.
- Frey, Bruno S.; Osterloh, Margit (2002). Successful Management by Motivation : Balancing Intrinsic and Extrinsic Incentives. Springer. p. 234. ISBN 3540424016. Retrieved 2013-07-11.
- Lawler, John; Bilson, Andy (2013). Social Work Management and Leadership : Managing Complexity with Creativity. Routledge. pp. 84–85. ISBN 1135247056. Retrieved 2013-07-14.
- Poister, Theodore H. (2008). Measuring Performance in Public and Nonprofit Organizations. John Wiley & Sons. p. 63. ISBN 047036517X. Retrieved 2013-07-14.
- Ryals, Lynette; McDonald, Malcolm (2012). Key Account Plans : The practitioners' guide to profitable planning. Routledge. p. 268. ISBN 1136390650. Retrieved 2013-07-14.
- Shahin, Arash; Mahbod, M. Ali (2004). "Prioritization of key performance indicators: An integration of analytical hierarchy process and goal setting". International Journal of Productivity and Performance Management. Emerald. 56 (3): 226–240. doi:10.1108/17410400710731437. Retrieved 2018-02-10.
- Siegert, Richard J; Taylor, William J (2004). "Theoretical aspects of goal-setting and motivation in rehabilitation". Disability & Rehabilitation. Informa. 26 (1): 1–8. doi:10.1080/09638280410001644932. Retrieved 2018-02-10.
- Dwyer, Judith; Hopwood, Nicole (2010). Management Strategies and Skills. McGraw-Hill. ISBN 9780070277670.
- "SMART objectives". Investors in People. Retrieved 10 September 2015.
- O'Neil, Jan; Conzemius, Anne (2006). The Power of SMART Goals : Using Goals to Improve Student Learning. Solution Tree Press. p. 33. ISBN 978-1-932127-87-4.
- Blanchard, Kenneth. One Minute Manager.
- Mentioned as an alternative in Yemm, Graham (2013)
- Mentioned as an alternative in Piskurich, George M. (2011)
- Mentioned as an alternative in Lawler, John; Bilson, Andy (2013)
- Blanchard, Kenneth. One Minute Manager.
- "SMART Requirements Definition and Management". www.esterline.com. Retrieved 2017-05-31.[dead link]
- "How to Write SMART Objectives" (PDF). Centers for Disease Control and Prevention.
- Brian Mac. "Goal Setting". Brian Mac Sports Coach. Archived from the original on 13 July 2017. Retrieved 25 June 2018.
- Atkinson, Marilyn; Chois, Rae T. (2012). Step-by-Step Coaching. Exalon Publishing, LTD. ISBN 978-0978370459.
- "Forget SMART Goals -- Try CLEAR Goals Instead".
- "Goal Setting - Are Your Goals SMART PURE and CLEAR".