In this guide

Tap +
Set the time
Choose the days
Check it is on
Delete: touch and hold
It is gone
If you do not see this option
If this does not work
Good to know
Sources

Short answer

Open Clock, Alarm and tap +. Turn the hour and minute wheels, pick Ring once, Weekdays or Custom, and tap Done. To delete, touch and hold the alarm and tap Delete: it goes at once, with no confirmation.

Device: Android
Shown on: OnePlus Nord 5 (CPH2709), OxygenOS 16.0.5.1201, Android 16
App: Clock
Path: Clock › Alarm
Real screenshots: 6 of 6 steps
Checked: October 2026
Sources: 2 official, linked below

Step by step

Tap +
Open Clock. On Alarm, tap the red + at the bottom.
Done
Set the time
Turn the wheels to the time: 06:15. The top says when it will ring next.
Done
Choose the days
Ring once, Weekdays, Scramble! or Custom. Below are Alarm name, Ringtone, Vibrate and Snooze. Tap Done.
Done
Check it is on
The new alarm is on, set to Ring once, and the top says Next alarm in 9 hours 25 minutes.
Done
Delete: touch and hold
The alarm is ticked, 1 selected. Tap Delete at the bottom.
Done
It is gone
The 06:15 alarm went at once. We saw no confirmation box and no Undo bar.
Done

If you do not see this option

Scramble!? One of the repeat choices on ours. We did not try it.
Older OxygenOS? OnePlus's OxygenOS 14 manual says the same: touch and hold an alarm to delete it. Source: OxygenOS 14.0 User Manual

If this does not work

Alarm silent? Check the Ringtone and the alarm volume. Source: Set, cancel, or snooze alarms on your Android device
Did not ring? Its switch must be on. Ours showed the switch on and Next alarm in 9 hours 25 minutes.
Deleted by mistake? There is no undo. Set it again.