Start event
Where a process begins. In BPMN the start event is a circle drawn with a single thin line.
Easily confused with
How to read it
BPMN 2.0.2, the Object Management Group’s standard, says the start event indicates where a particular process will start, and requires its line to stay thin so that it can be told apart from the intermediate and end events. Politecnico di Milano’s BPMN exercise book says every process starts with one and ends with an end event. A start event can only catch a trigger, not throw one. The circle is left open in the middle for a marker that names the trigger, such as an envelope for a message or a clock for a time.
Also searched as: bpmn start, bpmn start event, start event symbol, thin circle bpmn.
Look-alikes
The three event circles differ only in their line: thin for a start, double for an intermediate event and thick for an end event, as Marco Montali’s course slides at the Free University of Bozen-Bolzano sum them up. A UML activity diagram starts at a small filled dot, the initial node, and a flowchart at a rounded terminal.
Read next
- Next in BPMN symbolsIntermediate eventSomething that happens partway through a process, such as a message arriving or a deadline passing. The intermediate event is a circle drawn with a double thin line.
- UML activity diagrams start at a small filled dot.Initial nodeA small filled black circle is the initial node, where the flow of a UML activity diagram starts. In a state machine diagram the same dot is the initial pseudostate, with an arrow to the first state.
More BPMN symbols
The same shape elsewhere
Browse symbols drawn with circles.
Sources
- Business Process Model and Notation (BPMN), Version 2.0.2, OMG document formal/2013-12-09, December 2013 (also ISO/IEC 19510), Object Management Group, Sections 10.5.2 and 7.3.2 (Table 7.2)
- Business Process Modeling Notation (BPMN): Modeling Exercises, Cinzia Cappiello, Pierluigi Plebani and Monica Vitali, v.1.1, 2016 (CC BY-SA), Politecnico di Milano, Chapter 3, Events; Example 1.1
- Data and Process Modelling, 8a. BPMN: Basic Modelling, Marco Montali, lecture slides, A.Y. 2014/2015, Free University of Bozen-Bolzano, Slide 10, The Main Basic Elements
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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