diff --git a/2024/day03/.gitignore b/2024/day03/.gitignore
new file mode 100644
index 0000000..599be4e
--- /dev/null
+++ b/2024/day03/.gitignore
@@ -0,0 +1,4 @@
+*.beam
+*.ez
+/build
+erl_crash.dump
diff --git a/2024/day03/gleam.toml b/2024/day03/gleam.toml
new file mode 100644
index 0000000..99bc1ad
--- /dev/null
+++ b/2024/day03/gleam.toml
@@ -0,0 +1,21 @@
+name = "day03"
+version = "1.0.0"
+
+# Fill out these fields if you intend to generate HTML documentation or publish
+# your project to the Hex package manager.
+#
+# description = ""
+# licences = ["Apache-2.0"]
+# repository = { type = "github", user = "", repo = "" }
+# links = [{ title = "Website", href = "" }]
+#
+# For a full reference of all the available options, you can have a look at
+# https://gleam.run/writing-gleam/gleam-toml/.
+
+[dependencies]
+gleam_stdlib = ">= 0.34.0 and < 2.0.0"
+gleam_yielder = ">= 1.1.0 and < 2.0.0"
+gleam_regexp = ">= 1.0.0 and < 2.0.0"
+
+[dev-dependencies]
+gleeunit = ">= 1.0.0 and < 2.0.0"
diff --git a/2024/day03/manifest.toml b/2024/day03/manifest.toml
new file mode 100644
index 0000000..f59e95a
--- /dev/null
+++ b/2024/day03/manifest.toml
@@ -0,0 +1,15 @@
+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "gleam_regexp", version = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_regexp", source = "hex", outer_checksum = "A3655FDD288571E90EE9C4009B719FEF59FA16AFCDF3952A76A125AF23CF1592" },
+  { name = "gleam_stdlib", version = "0.45.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "206FCE1A76974AECFC55AEBCD0217D59EDE4E408C016E2CFCCC8FF51278F186E" },
+  { name = "gleam_yielder", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_yielder", source = "hex", outer_checksum = "8E4E4ECFA7982859F430C57F549200C7749823C106759F4A19A78AEA6687717A" },
+  { name = "gleeunit", version = "1.2.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleeunit", source = "hex", outer_checksum = "F7A7228925D3EE7D0813C922E062BFD6D7E9310F0BEE585D3A42F3307E3CFD13" },
+]
+
+[requirements]
+gleam_regexp = { version = ">= 1.0.0 and < 2.0.0" }
+gleam_stdlib = { version = ">= 0.34.0 and < 2.0.0" }
+gleam_yielder = { version = ">= 1.1.0 and < 2.0.0" }
+gleeunit = { version = ">= 1.0.0 and < 2.0.0" }
diff --git a/2024/day03/src/day03.gleam b/2024/day03/src/day03.gleam
new file mode 100644
index 0000000..d0a66c1
--- /dev/null
+++ b/2024/day03/src/day03.gleam
@@ -0,0 +1,77 @@
+import gleam/int
+import gleam/io
+import gleam/list
+import gleam/option.{None, Some}
+import gleam/regexp
+import gleam/string
+import gleam/yielder
+import stdin.{stdin}
+
+pub fn main() {
+  let memory =
+    stdin()
+    |> yielder.to_list
+    |> string.concat
+
+  part1(memory) |> int.to_string |> io.println
+  part2(memory) |> int.to_string |> io.println
+}
+
+fn part1(memory: String) -> Int {
+  let assert Ok(re) =
+    regexp.compile(
+      "mul\\((\\d{1,3}),(\\d{1,3})\\)",
+      regexp.Options(case_insensitive: False, multi_line: True),
+    )
+  regexp.scan(re, memory)
+  |> list.map(fn(m) {
+    list.map(m.submatches, fn(s) {
+      case s {
+        Some(n) -> int.parse(n)
+        None -> Error(Nil)
+      }
+    })
+  })
+  |> list.map(fn(x) {
+    let assert [Ok(a), Ok(b)] = x
+    a * b
+  })
+  |> int.sum
+}
+
+fn part2(memory: String) {
+  let assert Ok(re) =
+    regexp.compile(
+      "do\\(\\)|don't\\(\\)|mul\\((\\d{1,3}),(\\d{1,3})\\)",
+      regexp.Options(case_insensitive: False, multi_line: True),
+    )
+  regexp.scan(re, memory)
+  |> do(True)
+  |> list.map(fn(x) {
+    let assert Ok(a) = int.parse(x.0)
+    let assert Ok(b) = int.parse(x.1)
+    a * b
+  })
+  |> int.sum
+}
+
+fn do(matches: List(regexp.Match), enabled: Bool) -> List(#(String, String)) {
+  case matches {
+    [match, ..rest] ->
+      case match.content {
+        "do()" -> do(rest, True)
+        "don't()" -> do(rest, False)
+        _ ->
+          case enabled {
+            True ->
+              case match.submatches {
+                [Some(a), Some(b)] ->
+                  list.flatten([[#(a, b)], do(rest, enabled)])
+                _ -> panic as "Invalid submatches!"
+              }
+            False -> do(rest, enabled)
+          }
+      }
+    [] -> []
+  }
+}
diff --git a/2024/day03/src/stdin.gleam b/2024/day03/src/stdin.gleam
new file mode 100644
index 0000000..560c4ec
--- /dev/null
+++ b/2024/day03/src/stdin.gleam
@@ -0,0 +1,24 @@
+import gleam/dynamic
+import gleam/result
+import gleam/yielder
+
+@external(erlang, "io", "get_line")
+fn ffi_read_line(prompt: String) -> dynamic.Dynamic
+
+fn read_line() -> Result(String, Nil) {
+  ffi_read_line("")
+  |> dynamic.from()
+  |> dynamic.string()
+  |> result.replace_error(Nil)
+}
+
+fn assert_upwrap(res: Result(a, _)) -> a {
+  let assert Ok(a) = res
+  a
+}
+
+pub fn stdin() -> yielder.Yielder(String) {
+  yielder.repeatedly(read_line)
+  |> yielder.take_while(result.is_ok)
+  |> yielder.map(assert_upwrap)
+}