Must I stop at a Stop sign even if the road is clear in Northern Ireland?

Yes. At a Stop sign you must stop at the stop line even when the road appears completely clear.

The legal requirement is different from Give Way: the stop is mandatory, then you assess whether it is safe to proceed.

For “Must I stop at a Stop sign even if the road is clear in Northern Ireland?”, the wider Northern Ireland context is this: Northern Ireland's Highway Code uses signs, signals and road markings together, so the safest reading is always the exact sign at the location plus any lane arrows, plates or temporary traffic management. Rules expressed as ‘must’ or ‘must not’ are legal requirements; advisory wording can still be used as evidence when responsibility for a collision is considered.

For this exact question — “Must I stop at a Stop sign even if the road is clear in Northern Ireland?” — the practical point is: Stop where required, make effective observations and move only when the junction can be entered without causing another road user to alter course dangerously. The answer should be applied to the actual signs, conditions, licence wording or parking rules in force at the time, because temporary restrictions and individual DVA decisions can change the ordinary position.

This Northern Ireland-specific page on “Must I stop at a Stop sign even if the road is clear in Northern Ireland?” was checked against the attached official sources before publication, with nidirect/DVA and the Northern Ireland Highway Code used ahead of generic UK motoring articles. If the rule, road layout or personal licence condition changes, those primary sources are the ones to re-check.