React + TypeScript usage of className prop

You can use the HTMLAttributes type, for example:

class MyComponent extends React.Component<MyProps & React.HTMLAttributes<HTMLDivElement>, {}> {
    render() {
        return <div className={ this.props.className }>My Div</div>
    }
}

That way you can pass any of the properties that a html element might need.

If you only need the className property then you can do this:

class MyComponent extends React.Component<MyProps & { className: string }, {}> {
    render() {
        return <div className={ this.props.className }>My Div</div>
    }
}

Or simply add it to your MyProps type.