diff --git a/CHANGELOG.md b/CHANGELOG.md
index fad5ef05d..0538a2301 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,12 @@
 * Make forceExclude work with directly specified files.  
   [jimmya](https://github.com/jimmya)
   [#4609](https://github.com/realm/SwiftLint/issues/4609)
+  [#4609](https://github.com/realm/SwiftLint/issues/4609)
+
+* Adds `all` pseudo-rule for `opt_in_rules` - enables all opt in rules
+  that are not listed in `disabled_rules`  
+  [Martin Redington](https://github.com/mildm8nnered)
+  [#4540](https://github.com/realm/SwiftLint/issues/4540)
 
 * Separate analyzer rules as an independent section in the rule directory of
   the reference.  
diff --git a/README.md b/README.md
index 40d04a4ed..23ce3776a 100644
--- a/README.md
+++ b/README.md
@@ -483,7 +483,10 @@ run SwiftLint from. The following parameters can be configured:
 Rule inclusion:
 
 * `disabled_rules`: Disable rules from the default enabled set.
-* `opt_in_rules`: Enable rules that are not part of the default set.
+* `opt_in_rules`: Enable rules that are not part of the default set. The
+   special `all` rule will enable all opt in rules, except the rules
+   listed in `disabled_rules`. Analyzer rules will not be enabled by
+   `all`, but can be listed explicitly.
 * `only_rules`: Only the rules specified in this list will be enabled.
    Cannot be specified alongside `disabled_rules` or `opt_in_rules`.
 * `analyzer_rules`: This is an entirely separate list of rules that are only
diff --git a/Source/SwiftLintFramework/Extensions/Configuration+RulesMode.swift b/Source/SwiftLintFramework/Extensions/Configuration+RulesMode.swift
index 2b5b5ebd5..97f725b55 100644
--- a/Source/SwiftLintFramework/Extensions/Configuration+RulesMode.swift
+++ b/Source/SwiftLintFramework/Extensions/Configuration+RulesMode.swift
@@ -61,8 +61,19 @@ public extension Configuration {
                 self = .only(Set(onlyRules + analyzerRules))
             } else {
                 warnAboutDuplicates(in: disabledRules)
-                warnAboutDuplicates(in: optInRules + analyzerRules)
-                self = .default(disabled: Set(disabledRules), optIn: Set(optInRules + analyzerRules))
+
+                let effectiveOptInRules: [String]
+                if optInRules.contains(RuleIdentifier.all.stringRepresentation) {
+                    let allOptInRules = primaryRuleList.list.compactMap { ruleID, ruleType in
+                        ruleType is OptInRule.Type && !(ruleType is AnalyzerRule.Type) ? ruleID : nil
+                    }
+                    effectiveOptInRules = Array(Set(allOptInRules + optInRules))
+                } else {
+                    effectiveOptInRules = optInRules
+                }
+
+                warnAboutDuplicates(in: effectiveOptInRules + analyzerRules)
+                self = .default(disabled: Set(disabledRules), optIn: Set(effectiveOptInRules + analyzerRules))
             }
         }
 
diff --git a/Source/SwiftLintFramework/Extensions/Configuration+RulesWrapper.swift b/Source/SwiftLintFramework/Extensions/Configuration+RulesWrapper.swift
index c25d8c93c..c7456ac8f 100644
--- a/Source/SwiftLintFramework/Extensions/Configuration+RulesWrapper.swift
+++ b/Source/SwiftLintFramework/Extensions/Configuration+RulesWrapper.swift
@@ -49,7 +49,7 @@ internal extension Configuration {
             case var .default(disabledRuleIdentifiers, optInRuleIdentifiers):
                 customRulesFilter = { !disabledRuleIdentifiers.contains($0.identifier) }
                 disabledRuleIdentifiers = validate(ruleIds: disabledRuleIdentifiers, valid: validRuleIdentifiers)
-                optInRuleIdentifiers = validate(ruleIds: optInRuleIdentifiers, valid: validRuleIdentifiers)
+                optInRuleIdentifiers = validate(optInRuleIds: optInRuleIdentifiers, valid: validRuleIdentifiers)
                 resultingRules = allRulesWrapped.filter { tuple in
                     let id = type(of: tuple.rule).description.identifier
                     return !disabledRuleIdentifiers.contains(id)
@@ -113,6 +113,10 @@ internal extension Configuration {
         }
 
         // MARK: - Methods: Validation
+        private func validate(optInRuleIds: Set<String>, valid: Set<String>) -> Set<String> {
+            validate(ruleIds: optInRuleIds, valid: valid.union([RuleIdentifier.all.stringRepresentation]))
+        }
+
         private func validate(ruleIds: Set<String>, valid: Set<String>, silent: Bool = false) -> Set<String> {
             // Process invalid rule identifiers
             if !silent {
@@ -220,12 +224,12 @@ internal extension Configuration {
             validRuleIdentifiers: Set<String>
         ) -> RulesMode {
             let childDisabled = child.validate(ruleIds: childDisabled, valid: validRuleIdentifiers)
-            let childOptIn = child.validate(ruleIds: childOptIn, valid: validRuleIdentifiers)
+            let childOptIn = child.validate(optInRuleIds: childOptIn, valid: validRuleIdentifiers)
 
             switch mode { // Switch parent's mode. Child is in default mode.
             case var .default(disabled, optIn):
                 disabled = validate(ruleIds: disabled, valid: validRuleIdentifiers)
-                optIn = child.validate(ruleIds: optIn, valid: validRuleIdentifiers)
+                optIn = child.validate(optInRuleIds: optIn, valid: validRuleIdentifiers)
 
                 // Only use parent disabled / optIn if child config doesn't tell the opposite
                 return .default(