It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Goldman Sachs International Equity Insights I (GCIIX) has a 0.79% expense ratio and 0.75% management fee. GCIIX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. With yearly returns of 11.92% over the last five years, this fund clearly wins.

American Funds Fundamental Investors 529A (CFNAX): 0.61% expense ratio and 0.24% management fee. CFNAX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. With yearly returns of 14.37% over the last five years, CFNAX is an effectively diversified fund with a long reputation of solidly positive performance.

American Beacon Small Cap Value Y (ABSYX Quick QuoteABSYX - Free Report) . Expense ratio: 0.84%. Management fee: 0.7%. Five year annual return: 10.08%. ABSYX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion.

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.