Factual error: Think of the '100 billion dollars' scene in Austin Powers 2, where the President laughs because that kind of money doesn't even exist. You now have an idea how ridiculous it is that a twelfth century outlaw stealing tax money and robbing travellers could get anything like '4 million' as the scribe mentions. King Richard's ransom was only something like 100,000.
Continuity mistake: When Robin and Little John fight in the river Robin's hair changes from being dry to wet to dry again despite falling in the river several times.
Continuity mistake: When the soldiers are taking anything valuable out of a village church, when they put up a wanted poster outside, Robin shoots an arrow into the poster and then Little John rips it of the wall and shows it to the men. When someone says, "Give it back" the soldiers drop what they are holding, and the poster is still on the wall with the arrow through it. (01:00:00)
Continuity mistake: After stealing the treasure along with Tuck Robin and Crew open the chest soaking wet. A deleted scene in England - 'throwing the carriage into the lake' - made that bit of the film make no sense.
Plot hole: The Bishop in the film is performing the duties you would expect of someone in his position (giving mass, hearing confessions, performing weddings etc.) He has his own private chambers in the cathedral, refers to Robin as 'the boy I knew' and talks about hearing his Father's confession four months earlier; so he's been around for a while. The problem is the credits refer to him as the 'Bishop of Hereford'. No explanation is ever given for why the Bishop of a city 100 miles away is living and working in Nottingham rather than looking after his own diocese; or why the Bishop of Nottingham isn't around to look after his. (The Bishop of Hereford was an enemy of Robin Hood in the original ballads, and it's likely the filmmakers just gave that name to the Bishop in the film due to its familiarity, without thinking about the plot hole this creates).
Factual error: There is no reason why the executioner would have an axe just conveniently lying around on the scaffold to use on Will Scarlet. All the criminals were sentenced to hang, he wasn't expecting to behead anybody. (For those thinking this might just be a contingency - beheading as a punishment was only ever used on members of the nobility. It's not like the executioner or the Sheriff would have prepared this as a back up 'just in case' - public executions didn't work like that).
Revealing mistake: When Friar Tuck hits his head on an over-hanging branch whilst on his cart, it is really obvious his head comes into contact much earlier than the added sound effect and his eventual reaction would suggest. Plus the branch bends and flexes backwards an awful lot - it's not resistant enough to knock someone out as depicted.Andrew Upton
Continuity mistake: During the hanging scene, after Wolf attacks Will, when Will is brought to the front of the crowd the manner in which the two guards restrain him changes repeatedly between shots. (01:54:05)
Audio problem: When Robin and his men have Friar Tuck pulling the wagon you can hear the men singing, but in the shot facing them, their lips are not moving.
Continuity mistake: Wolf (the boy) has semi-long, shaggy hair that hangs over his ears and eyes. During the archery contest, however, when Robin has to distract him by flicking his ear with the end of an arrow, his hair has been carefully slicked back to expose his ear during the close-up. In the wide shots, his hair has been left shaggy and down.
Continuity mistake: When the sheriff's men come to take Marian, she defends herself with a rod from the fireplace that was roasting some meat. If the rod had been sitting in the fireplace even for a few minutes, it's probably too hot for her to hold.
Continuity mistake: When Robin and Azeem are about to be launched in the catapult, look at Azeem's sword. When he first gets in, the blade is facing down. It then cuts to Will, then back to Azeem, whose sword is now facing blade up. Then they are launched and Azeem lands with the sword blade down again.