diff --git a/lib/protocol/http/error.rb b/lib/protocol/http/error.rb
index 69dc2c6..5e5911f 100644
--- a/lib/protocol/http/error.rb
+++ b/lib/protocol/http/error.rb
@@ -22,15 +22,17 @@ class RemoteError < Error
 		# @deprecated Use {RefusedError} instead.
 		RequestRefusedError = RefusedError
 		
-		# Represents a bad request error (as opposed to a server error).
-		# This is used to indicate that the request was malformed or invalid.
+		# Marks errors which may indicate a malformed or invalid request when raised while processing an incoming request.
 		module BadRequest
 		end
 		
-		# Raised when a singleton (e.g. `content-length`) header is duplicated in a request or response.
-		class DuplicateHeaderError < Error
+		# Raised when an HTTP header is malformed or invalid. When raised while processing an incoming request, it may be treated as a bad request.
+		class InvalidHeaderError < Error
 			include BadRequest
-			
+		end
+		
+		# Raised when a singleton (e.g. `content-length`) header is duplicated in a request or response.
+		class DuplicateHeaderError < InvalidHeaderError
 			# @parameter key [String] The header key that was duplicated.
 			def initialize(key, existing_value, new_value)
 				super("Duplicate singleton header key: #{key.inspect}")
@@ -62,9 +64,7 @@ def detailed_message(highlight: false)
 		end
 		
 		# Raised when an invalid trailer header is encountered in headers.
-		class InvalidTrailerError < Error
-			include BadRequest
-			
+		class InvalidTrailerError < InvalidHeaderError
 			# @parameter key [String] The trailer key that is invalid.
 			def initialize(key)
 				super("Invalid trailer key: #{key.inspect}")
diff --git a/lib/protocol/http/header/accept.rb b/lib/protocol/http/header/accept.rb
index 358a27b..eb3dd8c 100644
--- a/lib/protocol/http/header/accept.rb
+++ b/lib/protocol/http/header/accept.rb
@@ -23,7 +23,7 @@ class Accept < Split
 					(?=,|\z)                  # Match until a comma or end of string
 				/x
 				
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				MEDIA_RANGE = /\A(?<type>#{TOKEN})\/(?<subtype>#{TOKEN})(?<parameters>.*)\z/
 				
diff --git a/lib/protocol/http/header/accept_charset.rb b/lib/protocol/http/header/accept_charset.rb
index 890d719..ac9eeb3 100644
--- a/lib/protocol/http/header/accept_charset.rb
+++ b/lib/protocol/http/header/accept_charset.rb
@@ -12,7 +12,7 @@ module HTTP
 		module Header
 			# The `accept-charset` header represents a list of character sets that the client can accept.
 			class AcceptCharset < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# https://tools.ietf.org/html/rfc7231#section-5.3.3
 				CHARSET = /\A(?<name>#{TOKEN})(;q=(?<q>#{QVALUE}))?\z/
diff --git a/lib/protocol/http/header/accept_encoding.rb b/lib/protocol/http/header/accept_encoding.rb
index d9fa98f..32e21c1 100644
--- a/lib/protocol/http/header/accept_encoding.rb
+++ b/lib/protocol/http/header/accept_encoding.rb
@@ -12,7 +12,7 @@ module HTTP
 		module Header
 			# The `accept-encoding` header represents a list of encodings that the client can accept.
 			class AcceptEncoding < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# https://tools.ietf.org/html/rfc7231#section-5.3.1
 				QVALUE = /0(\.[0-9]{0,3})?|1(\.[0]{0,3})?/
diff --git a/lib/protocol/http/header/accept_language.rb b/lib/protocol/http/header/accept_language.rb
index ee47bfd..2767bc6 100644
--- a/lib/protocol/http/header/accept_language.rb
+++ b/lib/protocol/http/header/accept_language.rb
@@ -12,7 +12,7 @@ module HTTP
 		module Header
 			# The `accept-language` header represents a list of languages that the client can accept.
 			class AcceptLanguage < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# https://tools.ietf.org/html/rfc3066#section-2.1
 				NAME = /\*|[A-Z]{1,8}(-[A-Z0-9]{1,8})*/i
diff --git a/lib/protocol/http/header/digest.rb b/lib/protocol/http/header/digest.rb
index 7a6b63d..10851e9 100644
--- a/lib/protocol/http/header/digest.rb
+++ b/lib/protocol/http/header/digest.rb
@@ -23,7 +23,7 @@ module Header
 			# # => "sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=, md5=9bb58f26192e4ba00f01e2e7b136bbd8"
 			# ```
 			class Digest < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# https://tools.ietf.org/html/rfc3230#section-4.3.2
 				ENTRY = /\A(?<algorithm>[a-zA-Z0-9][a-zA-Z0-9\-]*)\s*=\s*(?<value>.*)\z/
diff --git a/lib/protocol/http/header/range.rb b/lib/protocol/http/header/range.rb
index c017668..7fa3e58 100644
--- a/lib/protocol/http/header/range.rb
+++ b/lib/protocol/http/header/range.rb
@@ -10,7 +10,7 @@ module HTTP
 		module Header
 			# Represents a `range` request header.
 			class Range
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				TOKEN = /[!#$%&'*+\-.0-9A-Z^_`a-z|~]+/
 				HEADER = /\A(?<unit>#{TOKEN})=(?<ranges>.*)\z/
diff --git a/lib/protocol/http/header/server_timing.rb b/lib/protocol/http/header/server_timing.rb
index 74444aa..a5e5c4f 100644
--- a/lib/protocol/http/header/server_timing.rb
+++ b/lib/protocol/http/header/server_timing.rb
@@ -23,7 +23,7 @@ module Header
 			# # => "db;dur=53.2, cache;dur=12.1;desc=\"Redis lookup\""
 			# ```
 			class ServerTiming < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# https://www.w3.org/TR/server-timing/
 				METRIC = /\A(?<name>[a-zA-Z0-9][a-zA-Z0-9_\-]*)(;(?<parameters>.*))?\z/
diff --git a/lib/protocol/http/header/te.rb b/lib/protocol/http/header/te.rb
index 17c36a3..552d6f3 100644
--- a/lib/protocol/http/header/te.rb
+++ b/lib/protocol/http/header/te.rb
@@ -14,7 +14,7 @@ module Header
 			#
 			# The `te` header allows a client to indicate which transfer encodings it can handle, and in what order of preference using quality factors.
 			class TE < Split
-				ParseError = Class.new(Error)
+				ParseError = Class.new(InvalidHeaderError)
 				
 				# Transfer encoding token pattern
 				TOKEN = /[!#$%&'*+\-.0-9A-Z^_`a-z|~]+/
diff --git a/readme.md b/readme.md
index a91bd86..7ca6c33 100644
--- a/readme.md
+++ b/readme.md
@@ -30,6 +30,10 @@ Please see the [project documentation](https://socketry.github.io/protocol-http/
 
 Please see the [project releases](https://socketry.github.io/protocol-http/releases/index) for all releases.
 
+### Unreleased
+
+  - Introduce `Protocol::HTTP::InvalidHeaderError` for malformed or invalid headers, which can be treated as bad requests.
+
 ### v0.71.0
 
   - Parse all cookie pairs from `Cookie` header fields, including multiple semicolon-separated pairs within each field.
diff --git a/releases.md b/releases.md
index d9e5b16..fd69e31 100644
--- a/releases.md
+++ b/releases.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
   - Clarified body stream lifecycle and ownership, including the directional semantics of `Protocol::HTTP::Body::Stream#close_read`, `#close_write`, and `#close`, how premature input closure affects the associated HTTP exchange, and ownership of streams passed to `Streamable#call`.
+  - Introduce `Protocol::HTTP::InvalidHeaderError` for malformed or invalid headers, which can be treated as bad requests.
 
 ## v0.71.0
 
diff --git a/test/protocol/http/error.rb b/test/protocol/http/error.rb
index f4bcd19..a5929a8 100644
--- a/test/protocol/http/error.rb
+++ b/test/protocol/http/error.rb
@@ -37,6 +37,18 @@
 	end
 end
 
+describe Protocol::HTTP::InvalidHeaderError do
+	let(:error) {subject.new("Invalid header.")}
+	
+	it "is an HTTP error" do
+		expect(error).to be_a(Protocol::HTTP::Error)
+	end
+	
+	it "can be treated as a bad request" do
+		expect(error).to be_a(Protocol::HTTP::BadRequest)
+	end
+end
+
 describe Protocol::HTTP::DuplicateHeaderError do
 	let(:key) {"content-length"}
 	let(:existing_value) {"100"}
@@ -44,6 +56,10 @@
 	let(:error) {subject.new(key, existing_value, new_value)}
 	
 	with "#initialize" do
+		it "is an invalid header error" do
+			expect(error).to be_a(Protocol::HTTP::InvalidHeaderError)
+		end
+		
 		it "should set the key and values" do
 			expect(error.key).to be == key
 			expect(error.existing_value).to be == existing_value
@@ -73,3 +89,11 @@
 		end
 	end
 end
+
+describe Protocol::HTTP::InvalidTrailerError do
+	let(:error) {subject.new("content-length")}
+	
+	it "is an invalid header error" do
+		expect(error).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+end
diff --git a/test/protocol/http/header/accept.rb b/test/protocol/http/header/accept.rb
index d650b9f..5b6c8c7 100644
--- a/test/protocol/http/header/accept.rb
+++ b/test/protocol/http/header/accept.rb
@@ -26,6 +26,10 @@
 end
 
 describe Protocol::HTTP::Header::Accept do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	let(:media_ranges) {header.preferred_media_ranges}
 	
diff --git a/test/protocol/http/header/accept_charset.rb b/test/protocol/http/header/accept_charset.rb
index b89d8e1..64738c1 100644
--- a/test/protocol/http/header/accept_charset.rb
+++ b/test/protocol/http/header/accept_charset.rb
@@ -19,6 +19,10 @@
 end
 
 describe Protocol::HTTP::Header::AcceptCharset do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	let(:charsets) {header.preferred_charsets}
 	
diff --git a/test/protocol/http/header/accept_encoding.rb b/test/protocol/http/header/accept_encoding.rb
index 836e569..85096be 100644
--- a/test/protocol/http/header/accept_encoding.rb
+++ b/test/protocol/http/header/accept_encoding.rb
@@ -19,6 +19,10 @@
 end
 
 describe Protocol::HTTP::Header::AcceptEncoding do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	let(:encodings) {header.preferred_encodings}
 	
diff --git a/test/protocol/http/header/accept_language.rb b/test/protocol/http/header/accept_language.rb
index 6bb3e11..183befd 100644
--- a/test/protocol/http/header/accept_language.rb
+++ b/test/protocol/http/header/accept_language.rb
@@ -19,6 +19,10 @@
 end
 
 describe Protocol::HTTP::Header::AcceptLanguage do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	let(:languages) {header.preferred_languages}
 	
diff --git a/test/protocol/http/header/digest.rb b/test/protocol/http/header/digest.rb
index 1ebef76..ad55c7d 100644
--- a/test/protocol/http/header/digest.rb
+++ b/test/protocol/http/header/digest.rb
@@ -7,6 +7,10 @@
 require "sus"
 
 describe Protocol::HTTP::Header::Digest do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	
 	with "empty header" do
diff --git a/test/protocol/http/header/range.rb b/test/protocol/http/header/range.rb
index 4ec8220..b36973e 100644
--- a/test/protocol/http/header/range.rb
+++ b/test/protocol/http/header/range.rb
@@ -6,6 +6,10 @@
 require "protocol/http/header/range"
 
 describe Protocol::HTTP::Header::Range do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	with ".parse" do
 		it "parses byte ranges" do
 			header = subject.parse("bytes=0-4, 10-, -5")
diff --git a/test/protocol/http/header/server_timing.rb b/test/protocol/http/header/server_timing.rb
index 6aa336b..fd5d0d1 100644
--- a/test/protocol/http/header/server_timing.rb
+++ b/test/protocol/http/header/server_timing.rb
@@ -7,6 +7,10 @@
 require "sus"
 
 describe Protocol::HTTP::Header::ServerTiming do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	
 	with "empty header" do
diff --git a/test/protocol/http/header/te.rb b/test/protocol/http/header/te.rb
index 5dde573..3c5303c 100644
--- a/test/protocol/http/header/te.rb
+++ b/test/protocol/http/header/te.rb
@@ -6,6 +6,10 @@
 require "protocol/http/header/te"
 
 describe Protocol::HTTP::Header::TE do
+	it "classifies parse errors as invalid headers" do
+		expect(subject::ParseError.new).to be_a(Protocol::HTTP::InvalidHeaderError)
+	end
+	
 	let(:header) {subject.parse(description)}
 	
 	with "chunked" do