Ahead of the Sheffield, Glasgow and London derbies live on Sky Sports this weekend, we've worked out which derbies are the most competitive in England and Scotland...
A Sky Sports panel selected 20 derby clashes across the two countries' leagues, of which we have calculated which have the closest all-time head-to-head league records.
According to our sums, the Black Country derby between West Brom and Wolves is the most competitive all-time derby from the list, with West Brom edging their rivals by a slender two-game margin - winning 54 and losing 52.
Blackburn are two tiers below Premier League rivals Burnley - but the League One side snatch the head-to-head victory by a narrow win/ loss ratio of 38-36.
The Tyne-Wear derby is the next most competitive fixture, with Newcastle claiming marginal head-to-head bragging rights over Sunderland.
In addition to winning promotion to the Premier League while Sunderland suffered relegation to the Championship, the Magpies have won 51 derbies since 1898, compared with Sunderland's 47 wins.
In Wales, Swansea and Cardiff have a competitive history - but the Swans have a 21-19 all-time win advantage.
In the East Midlands, Nottingham Forest and Derby County has, historically, also been a close affair with Forest narrowly edging head-to-heads 36-32 for wins from 90 meetings.
The 309th Old Firm league derby will play out live on Sky Sports at Ibrox this Saturday and, historically, it's the sixth most competitive derby on our list.
Rangers have won more top-flight titles than any other team in the world with 54 triumphs and have defeated their Glasgow neighbours on 119 occasions in the league since 1890.
Despite that historic dominance, Celtic have won 103 head-to-heads and have hogged the Premiership trophy for the last six successive seasons - since Rangers won their most recent crown in 2010/11.
Sheffield United gained automatic promotion to the Championship last season after winning the League One title and will face rivals Sheffield Wednesday at Hillsborough for the first time since 2012 on Sunday, live on Sky Sports.
Despite spending the last six seasons in England's third tier, United fans have the bragging rights for league derby wins with a 42-36 victory - while another 36 meetings have ended in a draw.
Including non-competitive and cup games, the two clubs have both won 48 derbies - meaning one side could claim an all-time advantage for that record with three points this weekend.
West Ham host Tottenham live on Sky Sports this Saturday, but the London rivals are now twice the distance apart at their new stadiums than when both clubs occupied Upton Park and White Hart Lane, respectively - currently separated by 12 miles as the crow flies.
However, Spurs have a greater margin of separation in terms of results, winning 53 derbies compared with West Ham's 44 victories.
MOST DOMINANT
Chelsea are the derby kings for dominance over a local rival, with a 41-7 derby win record against neighbours Fulham, while Southampton also reign supreme over south-coast rivals Portsmouth with a 14-8 lead.
In Scotland, Hearts have a 119-69 win/ loss ratio against Hibernian from 272 league meetings, with 84 ending in a draw, while Dundee United also have historic dominance over rivals Dundee.
The Manchester clubs are both considered among the favourites to win the Premier League this term - but United boast a considerable 61-44 winning margin over City since 1894, while Bristol City have a 34-24 win/ loss ratio over Bristol Rovers.
Can Celtic and Sheffield Wednesday convert their recent league dominance and reduce head-to-head deficits against rivals Rangers and Sheffield United this weekend? And can Tottenham extend their impressive record against the Hammers?
Watch Rangers v Celtic live on Sky Sports Football or West Ham v Tottenham live on Sky Sports Premier League from 11.30am on Saturday and Sheffield Wednesday v Sheffield United live on Sky Sports Football from 12.30pm on Sunday