Charlize Theron has the ''mouth of a sailor''.

The 42-year-old actress shocked her 'Gringo' co-star David Oyelowo with her ''foul-mouthed'' use of language because he thought she seemed ''debonair and elegant'', but he enjoyed the fact she doesn't feel the need to censor herself for anyone.

He told E! News: ''She's pretty foul-mouthed. That's something from day one I was like, 'Wow!'

''Especially because she's so debonair and elegant, and then she has the mouth of the sailor.

''But I love her for the fact that she's always 100 percent herself. She's one of the bravest people I know.''

And Charlize admitted she is a ''big lover'' of the word f**k, but insisted she doesn't always use the profanity for everyone to hear.

She said: ''There are variations of it, motherf***er, f**k you.

''There are many variations you can go with. I tend to say it under my breath.''

However, the 'Fate of the Furious' star insisted she moderates her language around her two children, son Jackson, six, and two-year-old daughter August, though the occasional expletive does still slip out.

She said: ''I know what my responsibilities are as a parent.

''It's not like the truck driver comes home. I've definitely stubbed my toe and said s**t or something like that and my kids are like, 'Mom!' ''

But Charlize doesn't want to hear her kids swear until they are much older.

She recalled telling them: ''Listen, we don't have a swear jar. This is how adults speak sometimes. One day when you're an adult, you'll get to speak like this. But not now.''

Meanwhile, the 'Atomic Blonde' star recently spoke of how much she used to enjoy smoking marijuana.

She said: ''I was a wake-and-baker for most of my life.

''I was older [when I first tried it]. I didn't really mess around with anything until I was much older. But I really appreciated marijuana way more than alcohol or anything else.''

However, the 'Gringo' actress stopped using the drug in her early thirties when she realised it had made her ''boring''.

She added in an interview with E! News: ''My chemistry was really good with it when I was younger and then it just changed one day.

''Like, in my early thirties I just became boring on it and I would just stand in front of my fridge, so that's no good.

''It totally changed, so I stopped.''