How did they do it? Well Kidderminster, who play in the National League North, came from behind to beat Championship side Reading 2-1 at the Aggborough Stadium.
The dream of a 'Cupset' appeared over for the Worcestershire-based side when George Puscas put Veljko Paunovic's side ahead on the stoke of half time.
But to their credit, Kidderminster fought back splendidly with second-half goals from Sam Austin and Amari Morgan-Smith sealing a famous victory.
And National League Boreham Wood secured their place in the fourth round for the first time in their history as they won 2-0 at home to AFC Wimbledon, who play in League One.
Tyrone Marsh's spectacular first-half goal and Adrian Clifton's late strike, moments after coming off the bench, secured a 2-0 victory and one of the shocks of the third round against League One AFC Wimbledon.
The Dons, who in their previous incarnation caused probably the biggest upset of them all when they beat Liverpool in the 1988 final, for once found themselves on the wrong end of a cup surprise.
It was a memorable afternoon for Wood and their manager Luke Garrard, who as a player made more than 100 appearances for Wimbledon and helped them to two promotions, as he ended up dumping his old club out of the competition.
The phenomenal ties capped off a manic Saturday afternoon of third round action with League One Cambridge United sealing a famous 1-0 win over mega rich Newcastle.
Elsewhere, League Two Barrow, who played the majority of their tie at Barnsley with ten men, took the Championship side to extra-time with the scores finishing 4-4 in the 90. However, the Tykes ended up winning 5-4.
There were no problems for Brentford, who breezed to a 4-1 win at Port Vale, while Leicester were victors by the same scoreline in an all-Premier League tie against Watford.
Brighton survived a scare at West Brom as they came from behind to win 2-1 after extra-time.
Earlier on Saturday, Burnley were the first Premier League casualty with a defeat at home to Huddersfield while League Two Hartlepool got the better of Blackpool, who play in the Championship.
Below you can see the full-time scores for all the FA Cup third round ties so far.