diff --git a/app/models/archived_patient.rb b/app/models/archived_patient.rb
index 5ead4aebb..0a31000fe 100644
--- a/app/models/archived_patient.rb
+++ b/app/models/archived_patient.rb
@@ -6,6 +6,7 @@ class ArchivedPatient < ApplicationRecord
   include PaperTrailable
   include Exportable
   include LastMenstrualPeriodMeasureable
+  include Autodeletable
 
   # Relationships
   belongs_to :clinic, optional: true
diff --git a/app/models/concerns/autodeletable.rb b/app/models/concerns/autodeletable.rb
new file mode 100644
index 000000000..589bfa485
--- /dev/null
+++ b/app/models/concerns/autodeletable.rb
@@ -0,0 +1,32 @@
+# Allows models to be deleted after some period of time
+# By making this a concern, we can reuse the same code for Patients and
+# ArchivedPatients
+module Autodeletable
+    extend ActiveSupport::Concern
+
+    # instance method
+    def delete_date
+        # if config is blank, we return nil here
+        initial_call_date + Config.days_until_delete if Config.days_until_delete.present?
+    end
+
+    # This funny business allows us to call both Patient.autodelete! and
+    # ArchivedPatient.autodelete! without any extra code
+    # 
+    # (Any modules that include this Concern will get all methods in the
+    # ClassMethods module, below, as new class methods of their own!)
+    def self.included(base)
+        base.extend(ClassMethods)
+    end
+
+    module ClassMethods
+        def autodelete!
+            find_each do |p|
+                d = p.delete_date
+                # only delete if a delete date exists and is in the past.
+                p.destroy! if d.present? && d < Time.zone.today
+            end
+        end
+    end
+end
+
diff --git a/app/models/config.rb b/app/models/config.rb
index f8ba9b85d..316bd992d 100644
--- a/app/models/config.rb
+++ b/app/models/config.rb
@@ -22,7 +22,8 @@ class Config < ApplicationRecord
     hide_budget_bar: 'Enter "yes" to hide the budget bar display.',
     aggregate_statistics: 'Enter "yes" to show aggregate statistics on the budget bar.',
     hide_standard_dropdown_values: 'Enter "yes" to hide standard dropdown values. Only custom options (specified on this page) will be used.',
-    time_zone: "Time zone to use for displaying dates. Default is Eastern. Valid options are Eastern, Central, Mountain, Pacific, Alaska, Hawaii, Arizona, Indiana (East), or Puerto Rico."
+    time_zone: "Time zone to use for displaying dates. Default is Eastern. Valid options are Eastern, Central, Mountain, Pacific, Alaska, Hawaii, Arizona, Indiana (East), or Puerto Rico.",
+    days_until_delete: "Number of days (after initial entry) until patients are deleted. Leave blank to never delete old patients.",
   }.freeze
 
   enum config_key: {
@@ -46,7 +47,8 @@ class Config < ApplicationRecord
     aggregate_statistics: 17,
     hide_standard_dropdown_values: 18,
     county: 19,
-    time_zone: 20
+    time_zone: 20,
+    days_until_delete: 21,
   }
 
   # which fields are URLs (run special validation only on those)
@@ -100,6 +102,8 @@ class Config < ApplicationRecord
       [:validate_singleton, :validate_patient_archive],
     shared_reset:
       [:validate_singleton, :validate_shared_reset],
+    days_until_delete:
+      [:validate_singleton, :validate_number],
 
     hide_budget_bar:
       [:validate_singleton, :validate_yes_or_no],
@@ -161,6 +165,11 @@ def self.time_zone
     ActiveSupport::TimeZone.new(TIME_ZONE[tz])
   end
 
+  def self.days_until_delete
+    delete_days = Config.find_or_create_by(config_key: 'days_until_delete').options.try :last
+    delete_days.blank? ? nil : delete_days.to_i
+  end
+
   def self.archive_fulfilled_patients
     archive_days = Config.find_or_create_by(config_key: 'days_to_keep_fulfilled_patients').options.try :last
     # default 3 months
@@ -242,6 +251,7 @@ def titleize_capitalization
     end
 
     # generic validator for numerics
+    # note: this does NOT validate negative numbers or decimals
     def validate_number
       options.last =~ /\A\d+\z/
     end
diff --git a/app/models/patient.rb b/app/models/patient.rb
index d807d0d75..b8aadc158 100644
--- a/app/models/patient.rb
+++ b/app/models/patient.rb
@@ -14,6 +14,7 @@ class Patient < ApplicationRecord
   include Statusable
   include Exportable
   include EventLoggable
+  include Autodeletable
 
   # Callbacks
   before_validation :clean_fields
@@ -214,7 +215,7 @@ def archive_date
       initial_call_date + Config.archive_all_patients.days
     end
   end
-
+  
   def recent_history_tracks
     versions.where(updated_at: 6.days.ago..)
   end
@@ -294,4 +295,5 @@ def special_circumstances_length
       errors.add(:special_circumstances, 'is invalid') if value && value.length > 50
     end
   end
+
 end
diff --git a/lib/tasks/nightly_cleanup.rake b/lib/tasks/nightly_cleanup.rake
index 6348d4dff..904328555 100644
--- a/lib/tasks/nightly_cleanup.rake
+++ b/lib/tasks/nightly_cleanup.rake
@@ -29,6 +29,12 @@ task nightly_cleanup: :environment do
 
       ArchivedPatient.archive_eligible_patients!
       puts "#{Time.now} -- archived patients for today for fund #{fund.name}"
+
+      Patient.autodelete!
+      puts "#{Time.now} -- autodeleted old patients for fund #{fund.name}"
+
+      ArchivedPatient.autodelete!
+      puts "#{Time.now} -- autodeleted old archived patients for fund #{fund.name}"
     end
   end
 end
diff --git a/test/models/autodeletable_test.rb b/test/models/autodeletable_test.rb
new file mode 100644
index 000000000..fc10dfc2a
--- /dev/null
+++ b/test/models/autodeletable_test.rb
@@ -0,0 +1,112 @@
+require 'test_helper'
+
+class AutodeletableTest < ActiveSupport::TestCase
+    before do
+        @line = create :line, name: 'DC'
+        @pt_a = create :patient,
+                        name: 'Amanda',
+                        primary_phone: '222-222-2222',
+                        line: @line,
+                        initial_call_date: 10.days.ago
+        @pt_b = create :patient,
+                        name: 'Bethany',
+                        primary_phone: '333-333-3333',
+                        line: @line,
+                        initial_call_date: 0.days.ago
+        @pt_c = create :patient,
+                        name: 'Charley',
+                        primary_phone: '444-444-4444',
+                        line: @line,
+                        initial_call_date: 400.days.ago
+        @pt_d = create :archived_patient,
+                        line: @line,
+                        initial_call_date: 400.days.ago
+
+    end
+
+    # by default, no deletion: config is nil
+    describe 'without autodeletion' do
+        it 'should return nil deletion date' do
+            assert_nil Config.days_until_delete
+
+            assert_nil @pt_a.delete_date
+
+            assert_no_difference 'Patient.count' do
+                Patient.autodelete!
+            end
+
+            assert_no_difference 'ArchivedPatient.count' do
+                ArchivedPatient.autodelete!
+            end
+        end
+    end
+
+    describe 'with autodeletion' do
+        before do
+            c = Config.find_or_create_by(config_key: 'days_until_delete')
+            c.config_value = { options: ["100"] }
+            c.save!
+        end
+
+        it 'should only delete patients outside the window' do
+            assert_difference 'Patient.count', -1 do
+                Patient.autodelete!
+            end
+
+            # specifically, that should be pt_c
+            refute_includes Patient.all, @pt_c
+
+            assert_difference 'ArchivedPatient.count', -1 do
+                ArchivedPatient.autodelete!
+            end
+        end
+    end
+
+    describe 'edge cases' do
+        describe 'config 0 days' do
+            before do
+                c = Config.find_or_create_by(config_key: 'days_until_delete')
+                c.config_value = { options: ["0"] }
+                c.save!
+            end
+
+            it 'if config is 0, delete all patients now' do
+                Timecop.freeze(1.hour.ago) do
+                    Patient.autodelete!
+                    # delete doesn't occur because now hasn't happened yet ;)
+                    assert_equal 1, Patient.count
+                end
+
+                Timecop.freeze(1.day.after) do
+                    # later, now has happened
+                    Patient.autodelete!
+                    assert_equal 0, Patient.count
+                end
+            end
+        end
+        
+        describe 'nonzero config on the edge' do
+            before do
+                c = Config.find_or_create_by(config_key: 'days_until_delete')
+                c.config_value = { options: ["10"] }
+                c.save!
+            end
+
+            it 'deletes pt_a on the right day' do
+                Timecop.freeze(1.day.ago) do
+                    Patient.autodelete!
+                    assert_includes Patient.all, @pt_a
+                end
+
+                # present day - doesn't delete because <, not <=
+                Patient.autodelete!
+                assert_includes Patient.all, @pt_a
+
+                Timecop.freeze(1.day.after) do
+                    Patient.autodelete!
+                    refute_includes Patient.all, @pt_a
+                end       
+            end
+        end
+    end
+end
\ No newline at end of file
diff --git a/test/models/config_test.rb b/test/models/config_test.rb
index 984e02c38..27da39537 100644
--- a/test/models/config_test.rb
+++ b/test/models/config_test.rb
@@ -322,5 +322,30 @@ class ConfigTest < ActiveSupport::TestCase
       end
     end
 
+    describe 'days_util_default' do
+      it 'should default to nil' do
+        assert_nil Config.days_until_delete
+      end
+
+      it 'should validate bounds' do
+        c = Config.find_or_create_by(config_key: 'days_until_delete')
+
+        # non numeric
+        c.config_value = { options: ["a"] }
+        refute c.valid?
+
+        # negatives don't work
+        c.config_value = { options: ["-48"] }
+        refute c.valid?
+
+        # non-singleton
+        c.config_value = { options: ["1", "2"] }
+        refute c.valid?
+
+        # good
+        c.config_value = { options: ["10"] }
+        assert c.valid?
+      end
+    end
   end
 end