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 break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

MFS Blended Research Intl Eq R6 (BRXVX Quick QuoteBRXVX - Free Report) : 0.41% expense ratio and 0.35% management fee. BRXVX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets. BRXVX has achieved five-year annual returns of an astounding 12.65%.

Fidelity Large Cap Stock Fund (FLCSX): 0.75% expense ratio and 0.74% management fee. FLCSX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With yearly returns of 16.01% over the last five years, FLCSX is an effectively diversified fund with a long reputation of solidly positive performance.

Goldman Sachs LrgCp Gr Insights R6 (GLCUX) is an attractive large-cap allocation. GLCUX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. GLCUX has an expense ratio of 0.54%, management fee of 0.5%, and annual returns of 13.9% over the past five years.

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.