Here's a non-exhaustive list of essentials not to forget.

• Opt for a soft carry-on suitcase (78 cm x 38 cm) or a travel backpack, which are easier to fit in the vehicle, on horseback, or on pack yaks.
• A small day backpack for your daily essentials;
• Breathable underwear that dries quickly;
• City attire (optional);
• Light clothing and warm layers—temperature swings can be dramatic from one location to another, depending on climate and time of day;
• Fleece jacket, windbreaker, such as Polartec or Windpro;
• Comfortable trousers (trekking-style) for hiking and horseback riding;
• Thick socks and thermal leggings, just in case, in May and September;
• Waterproof, grip-soled hiking boots with ankle support that feel comfortable—avoid new shoes that risk causing blisters;
• A hat and scarf for cold snaps (except June 10 – August 20);
• Gloves, especially if you're riding;
• Waterproof jacket such as K-Way or Gore-tex. Avoid ponchos and loose-fitting rain gear that could frighten horses if you're riding;
• A scarf or bandana to protect from sun and dust, or a hat or cap;
• Sunglasses with UV protection (category 3 minimum);
• Sleeping bag liner;
• Biodegradable soap, shampoo, laundry detergent, and bath towels;
• Wet wipes and alcohol-based hand gel for convenience;
• Notebook and pencil;
• Spare batteries for cameras, or solar chargers;
• Camera protection—dust is everywhere;
• Small packets of tissues;
• Pocket knife or Swiss Army knife, lighter, thread, and needle—useful for any occasion;
• Trash bags to line your luggage and protect your belongings from unexpected downpours;
• Headlamp (more practical than handheld torches);
• Water bottle for horseback treks.

For multi-day horseback treks, you may also want to add:

• Riding boots
• Riding pants
• Sheepskin pad for your saddle (optional)

Note that luggage delays are common—baggage often arrives the day after you do, or in rare cases, two or three days later. To avoid any inconvenience, we recommend packing a change of clothes in your carry-on. When traveling as a couple or family, it's wise to distribute your belongings across different suitcases. That way, if one bag goes missing, you won't lose all of one person's items, but rather a few items from each person.

Please do not bring a new or luxury-brand suitcase. Mongolia is a dusty country, and baggage can sometimes be handled roughly.