The 20 year old signs until the end of the season for Swindon from non league side Poole Town for an undisclosed fee.
Austin has averaged more than a goal a game over the past season and a half. Last season he scored 46 goals in 46 games. Simon Cox only managed 32 goals last season. This season he has already scored 18 goals for Poole in the first 11 games.
Chairman Andrew Fitton said: "Charlie is a classic example of a player who 'slipped through the net' and has had to make it back the hard way. Whatever level of football he has played he has always been a goalscorer and we believe that he has the potential to score goals for Swindon Town."