お先に失礼します。 — Excuse me for leaving ahead of you. (Workplace · Greeting, Universal, JLPT N5)

Gesture & etiquette

Give a small bow toward nearby colleagues as you say this; if the office is large, a moderate volume announcement is acceptable (don't whisper); gather your belongings beforehand so you can bow and exit smoothly.

This phrase is mandatory when leaving the office before your colleagues — skipping it is considered rude. The literal meaning 'I am being rude by leaving first' acknowledges the implicit obligation in Japan to stay until everyone finishes. Colleagues reply with 'お疲れ様でした' (Thank you for your hard work). Never just quietly slip out.