diff --git a/app/jobs/audits_backfill_job.rb b/app/jobs/audits_backfill_job.rb
new file mode 100644
index 00000000000..0c44bf0a9e2
--- /dev/null
+++ b/app/jobs/audits_backfill_job.rb
@@ -0,0 +1,42 @@
+# Job to fill the user_past_usernames and user_past_emails tables using information from the audits table 
+class AuditsBackfillJob < RedisSetJob
+  queue_as :utilities
+
+  def self.base_key
+    "audits_backfill"
+  end
+
+  def self.job_size
+    1000
+  end
+
+  def self.batch_size
+    100
+  end
+
+  def perform_on_batch(user_ids)
+    # scans by users so audits can be taken from users and limited appropriately
+    User.where(id: user_ids).find_each do |user|
+      # gets past data audits within limits
+      past_data = user.audits.order(id: :desc).where(action: "update").limit(ArchiveConfig.USER_HISTORIC_VALUES_LIMIT).filter_map do |audit|
+        if audit.audited_changes.key?("login") && audit.audited_changes["login"].first.present?
+          { username: audit.audited_changes["login"].first, changed_at: audit.created_at }
+        elsif audit.audited_changes.key?("email") && audit.audited_changes["email"].first.present?
+          { email: audit.audited_changes["email"].first, changed_at: audit.created_at }
+        end
+      end
+      past_data = past_data.uniq { |audit| audit[:username] }
+        .reject { |audit| audit[:username] == user.login }
+      past_data = past_data.uniq { |audit| audit[:email] }
+        .reject { |audit| audit[:email] == user.email }
+      # adds each type of past data to the appropriate database table
+      past_data.each do |audit|
+        window = audit[:changed_at] - 60.seconds..audit[:changed_at] + 60.seconds
+        UserPastUsername.create!(user_id: user.id, username: audit[:username], changed_at: audit[:changed_at]) if audit.key?(:username) && !UserPastUsername.exists?(user_id: user.id, username: audit[:username], changed_at: window)
+        next unless audit.key?(:email)
+
+        UserPastEmail.create!(user_id: user.id, email_address: audit[:email], changed_at: audit[:changed_at]) unless UserPastEmail.exists?(user_id: user.id, email_address: audit[:email], changed_at: window)
+      end
+    end
+  end
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index e822a5d4eb9..5db26aab620 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -89,6 +89,10 @@ class User < ApplicationRecord
   has_many :skins, foreign_key: "author_id", dependent: :nullify
   has_many :work_skins, foreign_key: "author_id", dependent: :nullify
 
+  # the user's past credentials
+  has_many :user_past_emails, dependent: :destroy
+  has_many :user_past_usernames, dependent: :destroy
+
   before_update :add_renamed_at, if: :will_save_change_to_login?
   after_update :update_pseud_name
   after_update :send_wrangler_username_change_notification, if: :is_tag_wrangler?
@@ -96,7 +100,6 @@ class User < ApplicationRecord
   after_update :log_email_change, if: :saved_change_to_email?
   after_update :expire_caches
   before_destroy :remove_user_from_kudos
-
   # Extra callback to make sure readings are deleted in an order consistent
   # with the ReadingsJob.
   #
@@ -197,6 +200,14 @@ def unread_inbox_comments_count
     unread_inbox_comments.with_bad_comments_removed.count
   end
 
+  def past_emails
+    self.user_past_emails
+  end
+
+  def past_usernames
+    self.user_past_usernames
+  end
+
   scope :alphabetical, -> { order(:login) }
   scope :starting_with, ->(letter) { where("login like ?", "#{letter}%") }
   scope :valid, -> { where(banned: false, suspended: false) }
@@ -584,6 +595,7 @@ def log_change_if_login_was_edited
                      else
                        "Old Username: #{login_before_last_save}; New Username: #{login}"
                      end
+    user_past_usernames.create!(username: login_before_last_save, changed_at: self.updated_at)
     create_log_item(options)
   end
 
@@ -600,6 +612,7 @@ def log_email_change
       admin_id: current_admin&.id
     }
     options[:note] = "Change made by #{current_admin&.login}" if current_admin
+    user_past_emails.create!(email_address: email_before_last_save, changed_at: self.updated_at)
     create_log_item(options)
   end
 
diff --git a/app/models/user_past_email.rb b/app/models/user_past_email.rb
new file mode 100644
index 00000000000..732bac8c7df
--- /dev/null
+++ b/app/models/user_past_email.rb
@@ -0,0 +1,4 @@
+# Allows admins to track all past emails of a user
+class UserPastEmail < ApplicationRecord
+  belongs_to :user
+end
diff --git a/app/models/user_past_username.rb b/app/models/user_past_username.rb
new file mode 100644
index 00000000000..59e9e673a08
--- /dev/null
+++ b/app/models/user_past_username.rb
@@ -0,0 +1,4 @@
+# Allows admins to track all past usernames of a user
+class UserPastUsername < ApplicationRecord
+  belongs_to :user
+end
diff --git a/db/migrate/20260103083335_create_user_past_emails.rb b/db/migrate/20260103083335_create_user_past_emails.rb
new file mode 100644
index 00000000000..50b6a761d97
--- /dev/null
+++ b/db/migrate/20260103083335_create_user_past_emails.rb
@@ -0,0 +1,12 @@
+class CreateUserPastEmails < ActiveRecord::Migration[7.2]
+  def change
+    create_table :user_past_emails do |t|
+      t.references :user, null: false, foreign_key: true, type: :integer
+      
+      t.string :email_address
+      t.datetime :changed_at
+      
+      t.timestamps
+    end
+  end
+end
diff --git a/db/migrate/20260103083447_create_user_past_usernames.rb b/db/migrate/20260103083447_create_user_past_usernames.rb
new file mode 100644
index 00000000000..af18c549a98
--- /dev/null
+++ b/db/migrate/20260103083447_create_user_past_usernames.rb
@@ -0,0 +1,12 @@
+class CreateUserPastUsernames < ActiveRecord::Migration[7.2]
+  def change
+    create_table :user_past_usernames do |t|
+      t.references :user, null: false, foreign_key: true, type: :integer
+      
+      t.string :username
+      t.datetime :changed_at
+
+      t.timestamps
+    end
+  end
+end
diff --git a/lib/tasks/after_tasks.rake b/lib/tasks/after_tasks.rake
index 6582f19832a..e4210432854 100644
--- a/lib/tasks/after_tasks.rake
+++ b/lib/tasks/after_tasks.rake
@@ -629,5 +629,17 @@ namespace :After do
     end
     puts "Job complete."
   end
+
+  desc "Run backfill for user_past_emails and user_past_usernames"
+  task(backfill: :environment) do
+    User.find_in_batches.with_index do |batch, index|
+      REDIS_GENERAL.sadd?("audits_backfill", batch.map(&:id))
+      
+      batch_number = index + 1
+      puts "Batch #{batch_number} complete."
+    end
+    AuditsBackfillJob.spawn_jobs
+    puts "Backfill started and running on resque in background"
+  end
   # This is the end that you have to put new tasks above.
 end
diff --git a/spec/jobs/audits_backfill_job_spec.rb b/spec/jobs/audits_backfill_job_spec.rb
new file mode 100644
index 00000000000..459abe12888
--- /dev/null
+++ b/spec/jobs/audits_backfill_job_spec.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe AuditsBackfillJob do
+  let(:existing_user) { create(:user) }
+
+  context "when audits previously exist" do
+    before do
+      # Manually create audit record so user_past_usernames isn't updated
+      existing_user.audits.create!(action: "update", auditable: existing_user, user: existing_user,
+                                   auditable_id: existing_user.id, audited_changes: { "login" => ["old_login", existing_user.login] })
+      existing_user.audits.create!(action: "update", auditable: existing_user, user: existing_user,
+                                   auditable_id: existing_user.id, audited_changes: { "email" => ["old@example.com", existing_user.email] })
+    end
+
+    it "creates backfilled records in user_past_usernames" do
+      user_ids = [existing_user.id]
+      AuditsBackfillJob.new.perform_on_batch(user_ids)
+      expect(existing_user.past_usernames.last.username).to eq("old_login")
+    end
+
+    it "creates backfilled records in user_past_emails" do
+      user_ids = [existing_user.id]
+      AuditsBackfillJob.new.perform_on_batch(user_ids)
+      expect(existing_user.past_emails.last.email_address).to eq("old@example.com")
+    end
+
+    it "contains both backfilled and new changes" do
+      user_ids = [existing_user.id]
+      AuditsBackfillJob.new.perform_on_batch(user_ids)
+      old_username = existing_user.login
+      existing_user.update!(login: "new_login")
+      expect(existing_user.past_usernames.count).to eq(2)
+      expect(existing_user.past_usernames.last.username).to eq(old_username)
+      expect(existing_user.past_usernames.first.username).to eq("old_login")
+    end
+  end
+
+  it "doesn't create duplicate records" do
+    # change with update first, then run backfill
+    old_username = existing_user.login
+    existing_user.update!(login: "new_login")
+    user_ids = [existing_user.id]
+    AuditsBackfillJob.new.perform_on_batch(user_ids)
+
+    expect(existing_user.past_usernames.count).to eq(1)
+    expect(existing_user.past_usernames.last.username).to eq(old_username)
+  end
+  
+  it "handles audits with a empty field" do
+    existing_user.audits.create!(action: "update", auditable: existing_user, user: existing_user,
+                                 auditable_id: existing_user.id, audited_changes: { "email" => ["", existing_user.email] })
+    user_ids = [existing_user.id]
+    AuditsBackfillJob.new.perform_on_batch(user_ids)
+    expect(existing_user.past_emails.count).to eq(0)
+  end
+end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index d55c1bf1f3d..b00564fdfc1 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -254,6 +254,15 @@
         expect(existing_user.renamed_at).to eq(Time.current)
         expect(existing_user.admin_renamed_at).to be nil
       end
+      
+      it "records past username" do
+        freeze_time
+        existing_user.update!(login: "new_username")
+        user_change = existing_user.past_usernames.last
+        expect(user_change.user_id).to eq(existing_user.id)
+        expect(user_change.username).not_to eq("new_username")
+        expect(user_change.changed_at).to eq(Time.current)
+      end
 
       context "username was recently changed" do
         before do
@@ -340,6 +349,21 @@
         expect(log_item.admin_id).to be_nil
         expect(log_item.note).to eq("System Generated")
       end
+      
+      it "records previous email" do
+        old_email = existing_user.past_emails.last
+        expect(old_email.email_address).not_to eq(existing_user.email)
+        expect(old_email.user_id).to eq(existing_user.id)
+        expect(old_email.changed_at).to eq(existing_user.updated_at)
+      end
+      
+      it "doesn't record previous email before confirmation" do
+        old_email = existing_user.user_past_emails.last
+        existing_user.update!(email: "newemail2@example.com")
+        existing_user.reload
+        after_email = existing_user.user_past_emails.last
+        expect(old_email).to eq(after_email)
+      end
     end
 
     context "as an admin" do