diff --git a/Gemfile b/Gemfile
index 18442e3b0..abbd3332f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -21,6 +21,7 @@ gem 'telephone_number'
 gem 'time_diff'
 gem 'tzinfo-data'
 gem 'valid_email2'
+gem 'email-provider-info'
 # compress javascript config.assets.js_compressor
 gem 'uglifier'
 ##-- used for single column multiple binary flags in notification settings/feature flagging --##
diff --git a/Gemfile.lock b/Gemfile.lock
index 2f4da34e3..99e75b33c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -270,6 +270,7 @@ GEM
       concurrent-ruby (~> 1.0)
       http (>= 3.0)
       ruby2_keywords
+    email-provider-info (0.0.1)
     email_reply_trimmer (0.1.13)
     erubi (1.13.0)
     et-orbi (1.2.11)
@@ -1016,6 +1017,7 @@ DEPENDENCIES
   dotenv-rails (>= 3.0.0)
   down
   elastic-apm
+  email-provider-info
   email_reply_trimmer
   facebook-messenger
   factory_bot_rails (>= 6.4.3)
diff --git a/db/migrate/20251021082242_add_unique_index_to_companies_domain.rb b/db/migrate/20251021082242_add_unique_index_to_companies_domain.rb
new file mode 100644
index 000000000..2fb387242
--- /dev/null
+++ b/db/migrate/20251021082242_add_unique_index_to_companies_domain.rb
@@ -0,0 +1,16 @@
+class AddUniqueIndexToCompaniesDomain < ActiveRecord::Migration[7.1]
+  def up
+    remove_index :companies, name: 'index_companies_on_domain_and_account_id', if_exists: true
+
+    add_index :companies, [:account_id, :domain],
+              unique: true,
+              name: 'index_companies_on_account_and_domain',
+              where: 'domain IS NOT NULL'
+  end
+
+  def down
+    remove_index :companies, name: 'index_companies_on_account_and_domain', if_exists: true
+    add_index :companies, [:domain, :account_id],
+              name: 'index_companies_on_domain_and_account_id'
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 022a0101e..45165d5c5 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -577,8 +577,8 @@ ActiveRecord::Schema[7.1].define(version: 2025_10_22_152158) do
     t.bigint "account_id", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["account_id", "domain"], name: "index_companies_on_account_and_domain", unique: true, where: "(domain IS NOT NULL)"
     t.index ["account_id"], name: "index_companies_on_account_id"
-    t.index ["domain", "account_id"], name: "index_companies_on_domain_and_account_id"
     t.index ["name", "account_id"], name: "index_companies_on_name_and_account_id"
   end
 
diff --git a/enterprise/app/jobs/migration/company_account_batch_job.rb b/enterprise/app/jobs/migration/company_account_batch_job.rb
new file mode 100644
index 000000000..2e6c20f19
--- /dev/null
+++ b/enterprise/app/jobs/migration/company_account_batch_job.rb
@@ -0,0 +1,54 @@
+class Migration::CompanyAccountBatchJob < ApplicationJob
+  queue_as :low
+
+  def perform(account)
+    account.contacts
+           .where.not(email: nil)
+           .find_in_batches(batch_size: 1000) do |contact_batch|
+      process_contact_batch(contact_batch, account)
+    end
+  end
+
+  private
+
+  def process_contact_batch(contacts, account)
+    contacts.each do |contact|
+      next unless should_process?(contact)
+
+      company = find_or_create_company(contact, account)
+      # rubocop:disable Rails/SkipsModelValidations
+      contact.update_column(:company_id, company.id) if company
+      # rubocop:enable Rails/SkipsModelValidations
+    end
+  end
+
+  def should_process?(contact)
+    return false if contact.company_id.present?
+    return false if contact.email.blank?
+
+    Companies::BusinessEmailDetectorService.new(contact.email).perform
+  end
+
+  def find_or_create_company(contact, account)
+    domain = extract_domain(contact.email)
+    company_name = derive_company_name(contact, domain)
+
+    Company.find_or_create_by!(account: account, domain: domain) do |company|
+      company.name = company_name
+    end
+  rescue ActiveRecord::RecordNotUnique
+    # Race condition: Another job created it between our check and create
+    # just find the one that was created
+
+    Company.find_by(account: account, domain: domain)
+  end
+
+  def extract_domain(email)
+    email.split('@').last&.downcase
+  end
+
+  def derive_company_name(contact, domain)
+    contact.additional_attributes&.dig('company_name').presence ||
+      domain.split('.').first.tr('-_', ' ').titleize
+  end
+end
diff --git a/enterprise/app/jobs/migration/company_backfill_job.rb b/enterprise/app/jobs/migration/company_backfill_job.rb
new file mode 100644
index 000000000..db9a3370f
--- /dev/null
+++ b/enterprise/app/jobs/migration/company_backfill_job.rb
@@ -0,0 +1,17 @@
+class Migration::CompanyBackfillJob < ApplicationJob
+  queue_as :low
+
+  def perform
+    Rails.logger.info 'Starting company backfill migration...'
+    account_count = 0
+    Account.find_in_batches(batch_size: 100) do |accounts|
+      accounts.each do |account|
+        Rails.logger.info "Enqueuing company backfill for account #{account.id}"
+        Migration::CompanyAccountBatchJob.perform_later(account)
+        account_count += 1
+      end
+    end
+
+    Rails.logger.info "Company backfill migration complete. Enqueued jobs for #{account_count} accounts."
+  end
+end
diff --git a/enterprise/app/models/company.rb b/enterprise/app/models/company.rb
index 764cb2a9c..fde6cb122 100644
--- a/enterprise/app/models/company.rb
+++ b/enterprise/app/models/company.rb
@@ -12,9 +12,9 @@
 #
 # Indexes
 #
-#  index_companies_on_account_id             (account_id)
-#  index_companies_on_domain_and_account_id  (domain,account_id)
-#  index_companies_on_name_and_account_id    (name,account_id)
+#  index_companies_on_account_and_domain   (account_id,domain) UNIQUE WHERE (domain IS NOT NULL)
+#  index_companies_on_account_id           (account_id)
+#  index_companies_on_name_and_account_id  (name,account_id)
 #
 class Company < ApplicationRecord
   include Avatarable
@@ -24,6 +24,7 @@ class Company < ApplicationRecord
     with: /\A[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?(\.[a-zA-Z0-9]([a-zA-Z0-9-]*[a-zA-Z0-9])?)+\z/,
     message: I18n.t('errors.companies.domain.invalid')
   }
+  validates :domain, uniqueness: { scope: :account_id }, if: -> { domain.present? }
   validates :description, length: { maximum: Limits::COMPANY_DESCRIPTION_LENGTH_LIMIT }
 
   belongs_to :account
diff --git a/enterprise/app/services/companies/business_email_detector_service.rb b/enterprise/app/services/companies/business_email_detector_service.rb
new file mode 100644
index 000000000..422ef41c8
--- /dev/null
+++ b/enterprise/app/services/companies/business_email_detector_service.rb
@@ -0,0 +1,19 @@
+class Companies::BusinessEmailDetectorService
+  attr_reader :email
+
+  def initialize(email)
+    @email = email
+  end
+
+  def perform
+    return false if email.blank?
+
+    address = ValidEmail2::Address.new(email)
+    return false unless address.valid?
+    return false if address.disposable_domain?
+
+    provider = EmailProviderInfo.call(email)
+
+    provider.nil?
+  end
+end
diff --git a/lib/tasks/companies.rake b/lib/tasks/companies.rake
new file mode 100644
index 000000000..11fb5dc10
--- /dev/null
+++ b/lib/tasks/companies.rake
@@ -0,0 +1,12 @@
+namespace :companies do
+  desc 'Backfill companies from existing contact email domains'
+  task backfill: :environment do
+    puts 'Starting company backfill migration...'
+    puts 'This will process all accounts and create companies from contact email domains.'
+    puts 'The job will run in the background via Sidekiq'
+    puts ''
+    Migration::CompanyBackfillJob.perform_later
+    puts 'Company backfill job has been enqueued.'
+    puts 'Monitor progress in logs or Sidekiq dashboard.'
+  end
+end
diff --git a/spec/enterprise/jobs/migration/company_account_batch_job_spec.rb b/spec/enterprise/jobs/migration/company_account_batch_job_spec.rb
new file mode 100644
index 000000000..9a3e88c9d
--- /dev/null
+++ b/spec/enterprise/jobs/migration/company_account_batch_job_spec.rb
@@ -0,0 +1,120 @@
+require 'rails_helper'
+
+RSpec.describe Migration::CompanyAccountBatchJob, type: :job do
+  let(:account) { create(:account) }
+
+  describe '#perform' do
+    before do
+      # Stub EmailProvideInfo to control behavior in tests
+      allow(EmailProviderInfo).to receive(:call) do |email|
+        domain = email.split('@').last&.downcase
+        case domain
+        when 'gmail.com', 'yahoo.com', 'hotmail.com', 'uol.com.br'
+          'free_provider' # generic free provider name
+        end
+      end
+    end
+
+    context 'when contact has business email' do
+      let!(:contact) { create(:contact, account: account, email: 'user@acme.com') }
+
+      it 'creates a company and associates the contact' do
+        expect do
+          described_class.perform_now(account)
+        end.to change(Company, :count).by(1)
+        contact.reload
+        expect(contact.company).to be_present
+        expect(contact.company.domain).to eq('acme.com')
+        expect(contact.company.name).to eq('Acme')
+      end
+    end
+
+    context 'when contact has free email' do
+      let!(:contact) { create(:contact, account: account, email: 'user@gmail.com') }
+
+      it 'does not create a company' do
+        expect do
+          described_class.perform_now(account)
+        end.not_to change(Company, :count)
+        contact.reload
+        expect(contact.company_id).to be_nil
+      end
+    end
+
+    context 'when contact has company_name in additional_attributes' do
+      let!(:contact) do
+        create(:contact, account: account, email: 'user@acme.com', additional_attributes: { 'company_name' => 'Acme Corporation' })
+      end
+
+      it 'uses the saved company name' do
+        described_class.perform_now(account)
+        contact.reload
+        expect(contact.company.name).to eq('Acme Corporation')
+      end
+    end
+
+    context 'when contact already has a company' do
+      let!(:existing_company) { create(:company, account: account, domain: 'existing.com') }
+      let!(:contact) do
+        create(:contact, account: account, email: 'user@acme.com', company: existing_company)
+      end
+
+      it 'does not change the existing company' do
+        described_class.perform_now(account)
+        contact.reload
+        expect(contact.company_id).to eq(existing_company.id)
+      end
+    end
+
+    context 'when multiple contacts have the same domain' do
+      let!(:contact1) { create(:contact, account: account, email: 'user1@acme.com') }
+      let!(:contact2) { create(:contact, account: account, email: 'user2@acme.com') }
+
+      it 'creates only one company for the domain' do
+        expect do
+          described_class.perform_now(account)
+        end.to change(Company, :count).by(1)
+        contact1.reload
+        contact2.reload
+        expect(contact1.company_id).to eq(contact2.company_id)
+        expect(contact1.company.domain).to eq('acme.com')
+      end
+    end
+
+    context 'when contact has no email' do
+      let!(:contact) { create(:contact, account: account, email: nil) }
+
+      it 'skips the contact' do
+        expect do
+          described_class.perform_now(account)
+        end.not_to change(Company, :count)
+        contact.reload
+        expect(contact.company_id).to be_nil
+      end
+    end
+
+    context 'when processing large batch' do
+      before do
+        contacts_data = Array.new(2000) do |i|
+          {
+            account_id: account.id,
+            email: "user#{i}@company#{i % 100}.com",
+            name: "User #{i}",
+            created_at: Time.current,
+            updated_at: Time.current
+          }
+        end
+        # rubocop:disable Rails/SkipsModelValidations
+        Contact.insert_all(contacts_data)
+        # rubocop:enable Rails/SkipsModelValidations
+      end
+
+      it 'processes all contacts in batches' do
+        expect do
+          described_class.perform_now(account)
+        end.to change(Company, :count).by(100)
+        expect(account.contacts.where.not(company_id: nil).count).to eq(2000)
+      end
+    end
+  end
+end
diff --git a/spec/enterprise/jobs/migration/company_backfill_job_spec.rb b/spec/enterprise/jobs/migration/company_backfill_job_spec.rb
new file mode 100644
index 000000000..e60b84487
--- /dev/null
+++ b/spec/enterprise/jobs/migration/company_backfill_job_spec.rb
@@ -0,0 +1,31 @@
+require 'rails_helper'
+
+RSpec.describe Migration::CompanyBackfillJob, type: :job do
+  describe '#perform' do
+    it 'enqueues the job' do
+      expect { described_class.perform_later }
+        .to have_enqueued_job(described_class)
+        .on_queue('low')
+    end
+
+    context 'when accounts exist' do
+      let!(:account1) { create(:account) }
+      let!(:account2) { create(:account) }
+
+      it 'enqueues CompanyAccountBatchJob for each account' do
+        expect do
+          described_class.perform_now
+        end.to have_enqueued_job(Migration::CompanyAccountBatchJob)
+          .with(account1)
+          .and have_enqueued_job(Migration::CompanyAccountBatchJob)
+          .with(account2)
+      end
+    end
+
+    context 'when no accounts exist' do
+      it 'completes without error' do
+        expect { described_class.perform_now }.not_to raise_error
+      end
+    end
+  end
+end
diff --git a/spec/enterprise/services/companies/business_email_detector_service_spec.rb b/spec/enterprise/services/companies/business_email_detector_service_spec.rb
new file mode 100644
index 000000000..ceabfa905
--- /dev/null
+++ b/spec/enterprise/services/companies/business_email_detector_service_spec.rb
@@ -0,0 +1,99 @@
+require 'rails_helper'
+
+RSpec.describe Companies::BusinessEmailDetectorService, type: :service do
+  let(:service) { described_class.new(email) }
+
+  describe '#perform' do
+    context 'when email is from a business domain' do
+      let(:email) { 'user@acme.com' }
+      let(:valid_email_address) { instance_double(ValidEmail2::Address, valid?: true, disposable_domain?: false) }
+
+      before do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
+        allow(EmailProviderInfo).to receive(:call).with(email).and_return(nil)
+      end
+
+      it 'returns true' do
+        expect(service.perform).to be(true)
+      end
+    end
+
+    context 'when email is from gmail' do
+      let(:email) { 'user@gmail.com' }
+      let(:valid_email_address) { instance_double(ValidEmail2::Address, valid?: true, disposable_domain?: false) }
+
+      before do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
+        allow(EmailProviderInfo).to receive(:call).with(email).and_return('gmail')
+      end
+
+      it 'returns false' do
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email is from Brazilian free provider' do
+      let(:email) { 'user@uol.com.br' }
+      let(:valid_email_address) { instance_double(ValidEmail2::Address, valid?: true, disposable_domain?: false) }
+
+      before do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
+        allow(EmailProviderInfo).to receive(:call).with(email).and_return('uol')
+      end
+
+      it 'returns false' do
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email is disposable' do
+      let(:email) { 'user@mailinator.com' }
+      let(:disposable_email_address) { instance_double(ValidEmail2::Address, valid?: true, disposable_domain?: true) }
+
+      it 'returns false' do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(disposable_email_address)
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email is invalid format' do
+      let(:email) { 'invalid-email' }
+      let(:invalid_email_address) { instance_double(ValidEmail2::Address, valid?: false) }
+
+      it 'returns false' do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(invalid_email_address)
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email is nil' do
+      let(:email) { nil }
+
+      it 'remains false' do
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email is empty string' do
+      let(:email) { '' }
+
+      it 'returns false' do
+        expect(service.perform).to be(false)
+      end
+    end
+
+    context 'when email domain is uppercase' do
+      let(:email) { 'user@GMAIL.COM' }
+      let(:valid_email_address) { instance_double(ValidEmail2::Address, valid?: true, disposable_domain?: false) }
+
+      before do
+        allow(ValidEmail2::Address).to receive(:new).with(email).and_return(valid_email_address)
+        allow(EmailProviderInfo).to receive(:call).with(email).and_return('gmail')
+      end
+
+      it 'returns false (case insensitive)' do
+        expect(service.perform).to be(false)
+      end
+    end
+  end
+end