No Bra Day falls in the middle of Breast Cancer Awareness Month.
Today (October 13), women are encouraged to ditch their undies and spread the word on social media.
You can post your stories and pictures to Twitter using the hashtag #NoBraDay.
Health experts hope that the campaign will encourage more women to check their boobs.
As one in eight women develop breast cancer at some point in their lives, being able to spot the warning signs is important.
The British public are advised to be “breast aware”.
Getting to know your body parts will help you to notice if any changes take place.
The NHS explains: “Get to know what is normal for you – for instance, your breasts may look or feel different at different times of your life.
“This will make it much easier to spot potential problems.”
So which breast cancer symptoms should you always be wary of?
Here are eight signs of breast cancer you should never ignore:
1. Lump or thickening in your breast or armpit
2. Change to the skin of your breast
3. Changes in the shape or size of your breast
4. Dimpling of the skin or thickening in the breast tissue
5. A nipple that’s turned in (inverted)
6. A rash (like eczema) on the nipple
7. Nipple changes or discharge
8. Pain in your breast
While 90% of breast lumps aren’t cancerous, it’s always best to visit your local GP if you notice any of the above symptoms.
Your doctor will then examine you, before referring you to a specialist clinic if they believe you are at risk.
Experts then carry out a mammogram or ultrasound before any diagnoses are made.
For more information, visit the Cancer Research website.