Can I invest in real estate through my 401(k) using a REIT fund?

Often yes. Many 401(k) plans include a real estate or REIT index fund in their menu, which is one of the cleanest ways to get real estate exposure because REIT dividends are mostly taxed as ordinary income and a 401(k) shelters them from annual taxation. If your plan doesn't offer one, you can hold a REIT fund in an IRA instead, which is a natural tax-advantaged home for this asset class. Avoid the complexity and cost of a self-directed 401(k) or IRA buying physical property unless you truly know what you're doing, as those carry strict prohibited-transaction rules. Check your plan's fund lineup and expense ratios first, and consider whether the broad index funds you already hold provide enough real estate exposure.