diff --git a/Advent of Code/2023/day_09.py b/Advent of Code/2023/day_09.py
new file mode 100644
index 0000000..d136225
--- /dev/null
+++ b/Advent of Code/2023/day_09.py	
@@ -0,0 +1,82 @@
+from collections import defaultdict, deque
+from typing import TYPE_CHECKING
+
+import aoc_helper
+from aoc_helper import (
+    Grid,
+    PrioQueue,
+    SparseGrid,
+    decode_text,
+    extract_ints,
+    extract_iranges,
+    extract_ranges,
+    extract_uints,
+    frange,
+    irange,
+    iter,
+    list,
+    map,
+    range,
+    search,
+    tail_call,
+)
+
+raw = aoc_helper.fetch(9, 2023)
+
+
+def parse_raw(raw: str):
+    return raw
+
+
+data = parse_raw(raw)
+
+
+def find_diff_sequence(sequences: list[list[int]]) -> list[list[int]]:
+    s = []
+    for i in range(len(sequences[-1]) - 1):
+        s.append(sequences[-1][i + 1] - sequences[-1][i])
+    if all(a == 0 for a in s):
+        return [*sequences, s]
+    return find_diff_sequence([*sequences, s])
+
+
+# providing this default is somewhat of a hack - there isn't any other way to
+# force type inference to happen, AFAIK - but this won't work with standard
+# collections (list, set, dict, tuple)
+def part_one(data=data):
+    def find_next_term(line: str) -> int:
+        sequences = find_diff_sequence([list(map(int, line.split(" ")))])
+        next_add = 0
+        for sequence in sequences[::-1]:
+            next_add = sequence[-1] + next_add
+        return next_add
+
+    total = 0
+    for line in data.splitlines():
+        total += find_next_term(line)
+    return total
+
+aoc_helper.lazy_test(day=9, year=2023, parse=parse_raw, solution=part_one)
+
+
+# providing this default is somewhat of a hack - there isn't any other way to
+# force type inference to happen, AFAIK - but this won't work with standard
+# collections (list, set, dict, tuple)
+def part_two(data=data):
+    def find_prev_term(line: str) -> int:
+        sequences = find_diff_sequence([list(map(int, line.split(" ")))])
+        prev_add = 0
+        for sequence in sequences[::-1]:
+            prev_add = sequence[0] - prev_add
+        return prev_add
+
+    total = 0
+    for line in data.splitlines():
+        total += find_prev_term(line)
+    return total
+
+
+aoc_helper.lazy_test(day=9, year=2023, parse=parse_raw, solution=part_two)
+
+aoc_helper.lazy_submit(day=9, year=2023, solution=part_one, data=data)
+aoc_helper.lazy_submit(day=9, year=2023, solution=part_two, data=data)