diff --git a/app/models/upload.rb b/app/models/upload.rb
index 511177edc..1a5ac9a8e 100644
--- a/app/models/upload.rb
+++ b/app/models/upload.rb
@@ -6,6 +6,9 @@ class Upload < ApplicationRecord
 
   MAX_FILES_PER_UPLOAD = 100
 
+  # The maximum number of 'pending' or 'processing' media assets a single user can have at once.
+  MAX_QUEUED_ASSETS = 250
+
   attr_accessor :files
 
   belongs_to :uploader, class_name: "User"
@@ -19,6 +22,7 @@ class Upload < ApplicationRecord
   validates :source, format: { with: %r{\Ahttps?://}i, message: "is not a valid URL" }, if: -> { source.present? }
   validates :referer_url, format: { with: %r{\Ahttps?://}i, message: "is not a valid URL" }, if: -> { referer_url.present? }
   validate :validate_file_and_source, on: :create
+  validate :uploader_is_not_limited, on: :create
 
   after_create :async_process_upload!
 
@@ -64,6 +68,14 @@ class Upload < ApplicationRecord
         errors.add(:base, "No file or source given")
       end
     end
+
+    def uploader_is_not_limited
+      queued_asset_count = uploader.upload_media_assets.unfinished.count
+
+      if queued_asset_count > MAX_QUEUED_ASSETS
+        errors.add(:base, "You have too many images queued for upload (queued: #{queued_asset_count}; limit: #{MAX_QUEUED_ASSETS}). Try again later.")
+      end
+    end
   end
 
   concerning :SourceMethods do
diff --git a/app/models/upload_media_asset.rb b/app/models/upload_media_asset.rb
index 43d1b6334..ac8514a8c 100644
--- a/app/models/upload_media_asset.rb
+++ b/app/models/upload_media_asset.rb
@@ -23,6 +23,9 @@ class UploadMediaAsset < ApplicationRecord
     failed: 300,
   }
 
+  scope :unfinished, -> { where(status: %w[pending processing]) }
+  scope :finished, -> { where(status: %w[active failed]) }
+
   def self.visible(user)
     if user.is_admin?
       all
diff --git a/app/models/user.rb b/app/models/user.rb
index e3c9442d4..714904faa 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -109,6 +109,7 @@ class User < ApplicationRecord
   validate  :validate_custom_css, if: :custom_style_changed?
   before_validation :normalize_blacklisted_tags
   before_create :promote_to_owner_if_first_user
+
   has_many :artist_versions, foreign_key: :updater_id
   has_many :artist_commentary_versions, foreign_key: :updater_id
   has_many :comments, foreign_key: :creator_id
@@ -131,7 +132,6 @@ class User < ApplicationRecord
   has_many :purchased_upgrades, class_name: "UserUpgrade", foreign_key: :purchaser_id, dependent: :destroy
   has_many :user_events, dependent: :destroy
   has_one :active_ban, -> { active }, class_name: "Ban"
-
   has_one :email_address, dependent: :destroy
   has_many :api_keys, dependent: :destroy
   has_many :note_versions, :foreign_key => "updater_id"
@@ -145,6 +145,8 @@ class User < ApplicationRecord
   has_many :ip_bans, foreign_key: :creator_id
   has_many :tag_aliases, foreign_key: :creator_id
   has_many :tag_implications, foreign_key: :creator_id
+  has_many :uploads, foreign_key: :uploader_id, dependent: :destroy
+  has_many :upload_media_assets, through: :uploads, dependent: :destroy
   belongs_to :inviter, class_name: "User", optional: true
 
   accepts_nested_attributes_for :email_address, reject_if: :all_blank, allow_destroy: true