diff --git a/lib/ex_phone_number/extraction.ex b/lib/ex_phone_number/extraction.ex
index fefa832..878f6e1 100644
--- a/lib/ex_phone_number/extraction.ex
+++ b/lib/ex_phone_number/extraction.ex
@@ -232,4 +232,38 @@ defmodule ExPhoneNumber.Extraction do
         {false, number}
     end
   end
+
+  @doc """
+  Attempts to extract a valid number from a phone number that is too long to be
+  valid, and resets the PhoneNumber object passed in to that valid version. If
+  no valid number could be extracted, the PhoneNumber object passed in will not
+  be modified.
+
+  Implements `i18n.phonenumbers.PhoneNumberUtil.prototype.truncateTooLongNumber`
+  """
+  @spec truncate_too_long_number(%PhoneNumber{}) :: {boolean(), %PhoneNumber{}}
+  def truncate_too_long_number(%PhoneNumber{} = phone_number) do
+    if is_valid_number?(phone_number) do
+      {true, phone_number}
+    else
+      national_number = PhoneNumber.get_national_number_or_default(phone_number)
+      truncate_too_long_number(phone_number, national_number)
+    end
+  end
+
+  defp truncate_too_long_number(%PhoneNumber{} = phone_number, national_number) do
+    national_number = div(national_number, 10)
+    phone_number_copy = %PhoneNumber{phone_number | national_number: national_number}
+
+    cond do
+      national_number == 0 or is_possible_number_with_reason?(phone_number_copy) == ValidationResults.too_short() ->
+        {false, phone_number}
+
+      not is_valid_number?(phone_number_copy) ->
+        truncate_too_long_number(phone_number, national_number)
+
+      true ->
+        {true, phone_number_copy}
+    end
+  end
 end
diff --git a/lib/ex_phone_number/model/phone_number.ex b/lib/ex_phone_number/model/phone_number.ex
index c724807..483906b 100644
--- a/lib/ex_phone_number/model/phone_number.ex
+++ b/lib/ex_phone_number/model/phone_number.ex
@@ -32,6 +32,15 @@ defmodule ExPhoneNumber.Model.PhoneNumber do
     not is_nil(phone_number.country_code)
   end
 
+  @national_number_default 0
+  def get_national_number_or_default(phone_number = %PhoneNumber{}) do
+    if is_nil(phone_number.national_number) do
+      @national_number_default
+    else
+      phone_number.national_number
+    end
+  end
+
   @spec has_national_number?(%PhoneNumber{}) :: boolean()
   def has_national_number?(phone_number = %PhoneNumber{}) do
     not is_nil(phone_number.national_number)
diff --git a/test/ex_phone_number/extraction_test.exs b/test/ex_phone_number/extraction_test.exs
index bd71363..8d2a1c3 100644
--- a/test/ex_phone_number/extraction_test.exs
+++ b/test/ex_phone_number/extraction_test.exs
@@ -6,6 +6,7 @@ defmodule ExPhoneNumber.ExtractionTest do
   import ExPhoneNumber.Extraction
 
   alias ExPhoneNumber.Metadata
+  alias ExPhoneNumber.PhoneNumberFixture
   alias ExPhoneNumber.RegionCodeFixture
   alias ExPhoneNumber.Constants.CountryCodeSource
   alias ExPhoneNumber.Constants.ErrorMessages
@@ -233,4 +234,22 @@ defmodule ExPhoneNumber.ExtractionTest do
       assert CountryCodeSource.from_default_country() == phone_number.country_code_source
     end
   end
+
+  describe ".truncate_too_long_number/1" do
+    test "TruncateTooLongNumber" do
+      assert {true, PhoneNumberFixture.gb_toll_free()} == truncate_too_long_number(PhoneNumberFixture.gb_toll_free_too_long())
+
+      assert {true, PhoneNumberFixture.it_number2()} == truncate_too_long_number(PhoneNumberFixture.it_number2_too_long())
+
+      assert {true, PhoneNumberFixture.us_number()} == truncate_too_long_number(PhoneNumberFixture.us_long_number())
+
+      assert {true, PhoneNumberFixture.international_toll_free()} == truncate_too_long_number(PhoneNumberFixture.international_toll_free_too_long())
+
+      assert {true, PhoneNumberFixture.gb_toll_free()} == truncate_too_long_number(PhoneNumberFixture.gb_toll_free())
+
+      assert {false, PhoneNumberFixture.us_invalid_prefix()} == truncate_too_long_number(PhoneNumberFixture.us_invalid_prefix())
+
+      assert {false, PhoneNumberFixture.us_short_number()} == truncate_too_long_number(PhoneNumberFixture.us_short_number())
+    end
+  end
 end
diff --git a/test/support/phone_number_fixture.ex b/test/support/phone_number_fixture.ex
index a173404..3a48c4f 100644
--- a/test/support/phone_number_fixture.ex
+++ b/test/support/phone_number_fixture.ex
@@ -23,7 +23,7 @@ defmodule ExPhoneNumber.PhoneNumberFixture do
   def ad_number() do
     %PhoneNumber{
       country_code: 376,
-      national_number: 12345
+      national_number: 12_345
     }
   end
 
@@ -291,6 +291,13 @@ defmodule ExPhoneNumber.PhoneNumberFixture do
     }
   end
 
+  def gb_toll_free_too_long() do
+    %PhoneNumber{
+      country_code: 44,
+      national_number: 80_123_456_780_123
+    }
+  end
+
   def gb_shared_cost() do
     %PhoneNumber{
       country_code: 44,
@@ -357,6 +364,22 @@ defmodule ExPhoneNumber.PhoneNumberFixture do
     }
   end
 
+  def it_number2() do
+    %PhoneNumber{
+      country_code: 39,
+      national_number: 2_234_567_890,
+      italian_leading_zero: true
+    }
+  end
+
+  def it_number2_too_long() do
+    %PhoneNumber{
+      country_code: 39,
+      national_number: 2_234_567_890_123,
+      italian_leading_zero: true
+    }
+  end
+
   def it_premium() do
     %PhoneNumber{
       country_code: 39,
@@ -598,6 +621,13 @@ defmodule ExPhoneNumber.PhoneNumberFixture do
     }
   end
 
+  def us_short_number() do
+    %PhoneNumber{
+      country_code: 1,
+      national_number: 1_234
+    }
+  end
+
   def us_short_by_one_number() do
     %PhoneNumber{
       country_code: 1,
@@ -658,6 +688,13 @@ defmodule ExPhoneNumber.PhoneNumberFixture do
     }
   end
 
+  def us_invalid_prefix() do
+    %PhoneNumber{
+      country_code: 1,
+      national_number: 2_401_234_567
+    }
+  end
+
   def uz_fixed_line() do
     %PhoneNumber{
       country_code: 998,