The best fantasy football defenses find ways to dominate NFL games by providing important stats like sacks and turnovers. They can also capitalize on opportunities by converting some turnovers into defensive touchdowns. All of these factor into their fantasy scores each week and limit opposing offenses to as few points as possible.
It's important to remember that special teams units, especially their return teams, also play a role in fantasy defense's weekly score, primarily by potentially adding return touchdowns. Adding all of these statistics together provides their final fantasy output.
The best ones in fantasy football history have found an advantageous balance of all of them, including the following five who have scored the most fantasy points in a single NFL season.

#5 - 1986 Chicago Bears - 251 fantasy points
The 1985 Chicago Bears are considered the best team in their franchise's history, leading them to their only Super Bowl victory. They also featured one of the best defenses in NFL history. The following year, in 1986, they were just as good as the season before but got much less praise.
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#4 - 1984 Denver Broncos - 252 fantasy points
The Orange Crush defense is one of the most iconic units in NFL history as the best ones often seem to have a clever nickname. They dominated for the Denver Broncos for about a decade, with 1984 representing their best fantasy football season.
#3 - 1961 San Diego Chargers - 283 fantasy points
The San Diego Chargers set an NFL record with nine defensive touchdowns during the 1961 season. That record still stands more than 50 years later. It's a big reason they had one of the best defensive seasons in fantasy history.
#2 - 1985 Chicago Bears - 284 fantasy points
The great Monsters of the Midway defense makes its second appearance on this list, and the 1985 version should come as no surprise. They are among the most legendary units in NFL history and often rank among the best to ever take the field.
#1 - 1984 Seattle Seahawks - 288 fantasy points
It may be surprising to see the 1984 Seattle Seahawks top the list rather than some of the other iconic defenses from the league's history. Nevertheless, the Seahawks' balanced fantasy contributions got the job done. This includes ranking in the top 20 for most sacks in a season and the fourth-most defensive touchdowns.
Also Read: When should you pick defense in fantasy?
Top 5 defenses in fantasy football in 2023

#5 - Buffalo Bills
The Buffalo Bills have quietly been one of the most consistently valuable fantasy defenses in recent years. They've finished in the top ten fantasy points in the past four seasons. This includes excellent fourth-place finishes in the last two years.
#4 - New England Patriots
The New England Patriots have finished inside the top ten fantasy football defenses in each of the last two seasons. With Bill Belichick in charge, they should always be one of the better units in the league.
#3 - Philadelphia Eagles
The Philadelphia Eagles almost set the NFL record for team sacks last year, finishing with the third-highest single season total ever. They are returning the majority of the same pass rushers and should pressure opposing quarterbacks again.
#2 - San Francisco 49ers
Nick Bosa has impressively recorded 51 career sacks despite playing in just 60 games. He should be a Defensive Player of the Year candidate, and with an excellent cast around him, the San Francisco 49ers are one of the top fantasy football defenses to target.
#1 - Dallas Cowboys
In the last two seasons since drafting Micah Parsons, the Dallas Cowboys have finished in the top two fantasy football defenses. They also added Stephon Gilmore during the offseason, so there's little reason to expect anything but another dominant year.
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