In short
An enterprise risk assessment is the organisation-wide exercise that identifies, scores and prioritises every material risk against a single consistent methodology. It is what produces the heat map, the top 10 risk list and the board paper. The point is not to list every risk anyone can imagine - it is to give the executive committee a defensible view of what could stop the organisation hitting its objectives, ranked in a way different business units can be compared.
An enterprise risk assessment is a structured, organisation-wide exercise to identify, score and prioritise the risks that could prevent an organisation from achieving its strategic objectives. It covers every business unit and every risk category - strategic, operational, financial, regulatory, technology, people and reputational - and produces a single ranked view the board and executive can act on.
It is not the same as a project risk assessment (one piece of work), a process risk assessment (one workflow), or a control assessment (one control). Those exist further down the stack. The enterprise risk assessment sits at the top, and feeds the board pack, the strategic plan and the capital and resource decisions that follow from it.
Enterprise vs project risk assessment: the practical difference
The two are easy to confuse because the underlying mechanic - identify, score, treat, monitor - is the same. The difference is scope, audience and what the output is used for.
Project / process risk assessment
Bottom-up, narrow scope
Scope: a single project, process, change or control.
Audience: the project sponsor and the operational owner.
Used to: make a go/no-go decision, set mitigations, or escalate one specific issue.
Enterprise risk assessment
Top-down, organisation-wide
Scope: the whole organisation, every business unit, every risk category.
Audience: the executive committee, the risk committee and the board.
Used to: set the enterprise risk profile, prioritise capital and management attention, and demonstrate to regulators that risks are understood and within appetite.
In practice, the enterprise assessment consumes the outputs of the lower-level assessments. The project, process and control assessments produce the evidence; the enterprise assessment aggregates, normalises and ranks them so the board sees one consistent picture instead of fifteen incompatible ones.

