diff --git a/README.md b/README.md
index 10c0bbd8..862c38cb 100644
--- a/README.md
+++ b/README.md
@@ -636,6 +636,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 889. Construct Binary Tree from Preorder and Postorder Traversal | [Link](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/) | [Link](./lib/medium/889_construct_binary_tree_from_preorder_and_postorder_traversal.rb) | [Link](./test/medium/test_889_construct_binary_tree_from_preorder_and_postorder_traversal.rb) |
 | 890. Find and Replace Pattern                                    | [Link](https://leetcode.com/problems/find-and-replace-pattern/)                                    | [Link](./lib/medium/890_find_and_replace_pattern.rb)                                    | [Link](./test/medium/test_890_find_and_replace_pattern.rb)                                    |
 | 894. All Possible Full Binary Trees                              | [Link](https://leetcode.com/problems/all-possible-full-binary-trees/)                              | [Link](./lib/medium/894_all_possible_full_binary_trees.rb)                              | [Link](./test/medium/test_894_all_possible_full_binary_trees.rb)                              |
+| 901. Online Stock Span                                           | [Link](https://leetcode.com/problems/online-stock-span/)                                           | [Link](./lib/medium/901_online_stock_span.rb)                                           | [Link](./test/medium/test_901_online_stock_span.rb)                                           |
 
 ### Hard
 
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index 6162009e..199aeb38 100644
--- a/leetcode-ruby.gemspec
+++ b/leetcode-ruby.gemspec
@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '7.8.5'
+  s.version = '7.8.6'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/901_online_stock_span.rb b/lib/medium/901_online_stock_span.rb
new file mode 100644
index 00000000..53099912
--- /dev/null
+++ b/lib/medium/901_online_stock_span.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/online-stock-span/
+class StockSpanner
+  # Init
+  def initialize
+    @stack = []
+  end
+
+  # @param {Integer} price
+  # @return {Integer}
+  def next(price)
+    result = 1
+    result += @stack.delete_at(@stack.size - 1)[1] while !@stack.empty? && @stack.last[0] <= price
+    @stack << [price, result]
+
+    result
+  end
+end
diff --git a/test/medium/test_901_online_stock_span.rb b/test/medium/test_901_online_stock_span.rb
new file mode 100644
index 00000000..29ac62e3
--- /dev/null
+++ b/test/medium/test_901_online_stock_span.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/901_online_stock_span'
+require 'minitest/autorun'
+
+class OnlineStockSpanTest < ::Minitest::Test
+  def test_default_one
+    stock_spanner = ::StockSpanner.new
+
+    assert_equal(1, stock_spanner.next(100))
+    assert_equal(1, stock_spanner.next(80))
+    assert_equal(1, stock_spanner.next(60))
+    assert_equal(2, stock_spanner.next(70))
+    assert_equal(1, stock_spanner.next(60))
+    assert_equal(4, stock_spanner.next(75))
+    assert_equal(6, stock_spanner.next(85))
+  end
+end