Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

AQR Long-Short Equity Fund R6 (QLERX): 1.15% expense ratio and 1.1% management fee. QLERX is a Long Short - Equity option. These funds' investment strategy consists of minimizing overall market exposure, while at the same time taking long positions in equities that are expected to appreciate and short positions in equities that are projected to decline. With annual returns of 24.82% over the last five years, this fund is a winner.

American Funds Growth Portfolio R6 (RGWGX). Expense ratio: 0.02%. Management fee: 0%. RGWGX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. This fund has managed to produce a robust 10.02% over the last five years.

GMO Intl Developed Equity Alloc III (GIOTX Quick QuoteGIOTX - Free Report) : 0.01% expense ratio and 0% management fee. GIOTX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. With a five-year annual return of 15.7%, this fund is a well-diversified fund with a long track record of success.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.