diff --git a/benchmarks.yml b/benchmarks.yml
index 5b61fd2f..645c1e73 100644
--- a/benchmarks.yml
+++ b/benchmarks.yml
@@ -235,6 +235,14 @@ throw:
   single_file: true
   ractor: true
 
+#
+# Thread benchmarks
+#
+threads_io_with_cpu:
+  desc: Benchmark to test how long I/O takes to complete when there's a mix of IO-bound and CPU-bound threads.
+  category: thread
+  single_file: true
+
 #
 # Ractor scaling benchmarks
 #
diff --git a/benchmarks/threads_io_with_cpu.rb b/benchmarks/threads_io_with_cpu.rb
new file mode 100644
index 00000000..d44c7ea7
--- /dev/null
+++ b/benchmarks/threads_io_with_cpu.rb
@@ -0,0 +1,69 @@
+require_relative '../harness/loader'
+
+require "socket"
+num_cpu_threads = 1
+num_io_threads = 1
+
+server_started = false
+
+def start_tcp_server(&started)
+  Thread.new do
+    server = TCPServer.new('localhost', 0) # random open port
+    started.call(server.local_address.ip_port)
+
+    loop do
+      client = server.accept
+      client.close
+      # Don't get request or generate response, it makes the benchmark take too long
+    end
+  end
+end
+
+def open_tcp_connection(host, port)
+  TCPSocket.open(host, port) { }
+end
+
+def fib(n)
+  return n if n <= 1
+  fib(n - 1) + fib(n - 2)
+end
+
+server_started = false
+port = nil
+start_tcp_server do |server_port|
+  server_started = true
+  port = server_port
+end
+loop until server_started
+
+io_requests_threshold = 5 # per thread
+
+run_benchmark(5) do
+  io_threads = num_io_threads.times.map do
+    Thread.new do
+      io_requests_made = 0
+      loop do
+        open_tcp_connection("localhost", port)
+        io_requests_made += 1
+        if io_requests_made >= io_requests_threshold
+          break
+        end
+      end
+    end
+  end
+
+  stop_looping = false
+
+  cpu_threads = num_cpu_threads.times.map do
+    Thread.new do
+      loop do
+        fib(30)
+        break if stop_looping
+      end
+    end
+  end
+
+  io_threads.each(&:join)
+  stop_looping = true
+  cpu_threads.join
+end
diff --git a/lib/argument_parser.rb b/lib/argument_parser.rb
index e7a4cf4e..2429f5e1 100644
--- a/lib/argument_parser.rb
+++ b/lib/argument_parser.rb
@@ -68,7 +68,7 @@ def parse(argv)
         args.out_override = v
       end
 
-      opts.on("--category=headline,other,micro,ractor", "when given, only benchmarks with specified categories will run") do |v|
+      opts.on("--category=headline,other,micro,thread,ractor", "when given, only benchmarks with specified categories will run") do |v|
         args.categories += v.split(",")
         if args.categories == ["ractor"]
           args.harness = "harness-ractor"
diff --git a/test/run_benchmarks_integration_test.rb b/test/run_benchmarks_integration_test.rb
index 9cf5a888..73fd5cf2 100644
--- a/test/run_benchmarks_integration_test.rb
+++ b/test/run_benchmarks_integration_test.rb
@@ -56,7 +56,7 @@
     it 'benchmarks.yml has valid category values' do
       require 'yaml'
       data = YAML.load_file(@benchmarks_yml)
-      valid_categories = ['headline', 'micro', 'other']
+      valid_categories = ['headline', 'micro', 'thread', 'other']
 
       data.each do |name, metadata|
         if metadata['category']