diff --git a/reorg-backup.sh b/reorg-backup.sh
new file mode 100755
index 0000000..58ba053
--- /dev/null
+++ b/reorg-backup.sh
@@ -0,0 +1,117 @@
+#!/bin/bash
+# reorg-backup.sh — reorganize backup season files into astro-YEAR folders.
+#
+# Moves files from:
+#   <backup_root>/<cam>/Season/MvtN/YYYY-MM-DD_*
+# Into:
+#   <backup_root>/astro-YEAR/<cam>/Season/MvtN/YYYY-MM-DD_*
+#
+# Uses season_info.py to determine the correct ASTRO_YEAR from each file's date.
+# NEVER deletes anything — only moves files.
+#
+# Usage:
+#   ./reorg-backup.sh <backup_root> [--dry-run]
+#
+# Example:
+#   ./reorg-backup.sh ~/drives/data2-main --dry-run
+#   ./reorg-backup.sh ~/drives/data2-main
+
+set -euo pipefail
+
+SCRIPT_DIR="$(dirname "$(realpath "$0")")"
+source "$SCRIPT_DIR/sky-cam.conf"
+export TIMEZONE
+
+BACKUP_ROOT=""
+DRY_RUN=false
+
+while [[ $# -gt 0 ]]; do
+    case "$1" in
+        --dry-run) DRY_RUN=true; shift ;;
+        -*)        echo "Unknown option: $1"; exit 1 ;;
+        *)         BACKUP_ROOT="$1"; shift ;;
+    esac
+done
+
+if [ -z "$BACKUP_ROOT" ]; then
+    echo "Usage: $0 <backup_root> [--dry-run]"
+    echo "  e.g. $0 ~/drives/data2-main --dry-run"
+    exit 1
+fi
+
+BACKUP_ROOT="$(realpath "$BACKUP_ROOT")"
+
+$DRY_RUN && echo "DRY RUN — no files will be moved"
+echo "Backup root: $BACKUP_ROOT"
+echo ""
+
+moved=0
+skipped=0
+errors=0
+
+# Find all mp4 files in Season/MvtN directories (not already in astro-* dirs)
+while IFS= read -r -d '' src_file; do
+    filename="$(basename "$src_file")"
+
+    # Extract date: handles YYYY-MM-DD_ (underscore) prefix
+    date_str="${filename%%_*}"
+    if ! [[ "$date_str" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; then
+        echo "SKIP (unrecognised filename): $src_file"
+        (( skipped++ )) || true
+        continue
+    fi
+
+    # Get ASTRO_YEAR for this date
+    _info="$(python3 "$SCRIPT_DIR/season_info.py" "$date_str" 2>/dev/null)" || {
+        echo "SKIP (season_info.py failed for $date_str): $filename"
+        (( skipped++ )) || true
+        continue
+    }
+    eval "$_info"
+
+    # Reconstruct target path:
+    #   <backup_root>/astro-YEAR/<cam>/<Season>/Mvt<N>/<filename>
+    # Source path is:
+    #   <backup_root>/<cam>/<Season>/Mvt<N>/<filename>
+    rel_path="${src_file#$BACKUP_ROOT/}"          # e.g. north/Winter/Mvt1/2025-01-06_...
+    cam_and_below="${rel_path#*/}"                # e.g. Winter/Mvt1/2025-01-06_...  (strip cam)
+    cam_name="${rel_path%%/*}"                    # e.g. north
+
+    dest_dir="$BACKUP_ROOT/astro-${ASTRO_YEAR}/$cam_name/$(dirname "$cam_and_below")"
+    dest_file="$dest_dir/$filename"
+
+    if [ "$src_file" = "$dest_file" ]; then
+        (( skipped++ )) || true
+        continue
+    fi
+
+    if [ -f "$dest_file" ]; then
+        echo "EXISTS — skip: astro-${ASTRO_YEAR}/$cam_name/$cam_and_below"
+        (( skipped++ )) || true
+        continue
+    fi
+
+    echo "MOVE  astro-${ASTRO_YEAR}/$cam_name/$cam_and_below"
+
+    if ! $DRY_RUN; then
+        mkdir -p "$dest_dir"
+        if mv "$src_file" "$dest_file"; then
+            (( moved++ )) || true
+        else
+            echo "  ERROR: mv failed"
+            (( errors++ )) || true
+        fi
+    else
+        (( moved++ )) || true
+    fi
+
+done < <(find "$BACKUP_ROOT" \
+    -not -path "*/astro-*" \
+    -regextype posix-extended \
+    -regex ".*/[A-Z][a-z]+/Mvt[0-9]+/[0-9]{4}-[0-9]{2}-[0-9]{2}_.*\.mp4" \
+    -print0 | sort -z)
+
+echo ""
+echo "────────────────────────────────────────"
+echo "Moved: $moved   Skipped: $skipped   Errors: $errors"
+$DRY_RUN && echo "(dry run — re-run without --dry-run to move files)"