Arnold Schwarzenegger is the most accomplished bodybuilder in the history of the sport, his gym — Gold’s in Venice — is considered the mecca of bodybuilding … so it’s pretty stunning Arnold rolled up to the gym today but refused to go inside.

Arnold bicycled to Gold’s Tuesday morning for a workout, now that the gym’s back in business. He’s there like clockwork when it’s open, so Tuesday marked a big day for him.

When he got to the front desk he was informed people needed to wear masks when they entered and when they were in certain common areas, but they do NOT require members to wear masks when working out.

Fact is … Gold’s is complying with the law — State regulations do not require people wearing masks when they lift, but Arnold’s way more concerned about safety — when people moan, grunt and handle the same weights, it’s risky.

The 72-year-old movie star/bodybuilder/politician, we’re told, will stay clear of Gold’s until people start wearing masks on the floor — or when there’s a vaccine.

The good news for Arnold — he has a spectacular gym at home.